Compress PDF

Compress scanned and image-heavy PDFs in your browser. No upload required. Compress up to 20 PDFs at once and download as a ZIP. No account needed.

Free to use. Runs in your browser.

Compress scanned and image-heavy PDFs in your browser, no upload required.

Process up to 20 PDFs at once and download as a ZIP. Your files stay on your device throughout. Results depend on the source PDF and your quality setting.

Compression Quality

Custom Quality70%

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How PDF Compression Works

PDF compression sounds simple, but the technique behind meaningful file-size reduction is more nuanced than most people realise. This tool uses a render-and-reassemble pipeline.

Here's what happens step by step: the tool loads your PDF using pdf.js (Mozilla's open-source PDF renderer), then draws every page onto an invisible HTML Canvas element at your chosen resolution. Each canvas is exported as a JPEG image at the quality level you selected. Finally, these JPEG images are stitched back together into a brand-new PDF using pdf-lib.

This is a lossy compression method. Unlike lossless techniques, which reorganise internal PDF structures without touching pixel data, this approach recompresses the visual content of each page. The trade-off is that selectable text becomes rasterised (turned into an image), but image-heavy files can become much smaller.

Why image-heavy PDFs shrink more: A scanned document is often a collection of large image pages wrapped in a PDF container. When the tool re-renders these pages as optimised JPEGs, the savings can be large. Conversely, a text-heavy PDF with vector graphics is already very efficient, so there is less pixel data to reduce.

Compressing Scanned Documents

Scanned PDFs are the most common use case for this tool. A raw scan from a printer, phone scanner, or flatbed scanner saves each page as a large uncompressed image. Re-encoding that image as an optimised JPEG typically produces 60 to 80% file-size reduction, often shrinking a 20 MB scan bundle to 4 to 8 MB in one pass.

For the clearest result on scanned documents: use the Web preset if you are sharing the file by email or uploading it to a portal; use the Print preset if the recipient will review handwritten notes or small printed text and readability matters. The Web preset at 40% quality is still clear enough for most standard scans.

One thing to check before compressing a multi-page scan: if any pages are rotated, fix them first with the Organize PDF tool. Page rotation is not corrected during compression.

Quality Settings Explained

Choosing the right quality preset is the single most important decision when compressing a PDF. Here's what each setting actually does under the hood:

Preset	JPEG Quality	Render Scale	Typical Reduction	Good For
Web (40%)	~0.49	1.3×	60 to 80%	Email attachments, quick sharing, web uploads
Print (70%)	~0.72	1.7×	40 to 60%	Reports, presentations, general documents
Maximum (95%)	~0.88	1.9×	15 to 35%	High-quality prints, portfolios, photography

The custom slider lets you fine-tune beyond presets. A setting of 50 to 60% often balances visible quality and file size. Below 30%, text may become noticeably blurry. Above 90%, files usually stay larger because the tool keeps more visual detail.

Practical tip: Start with the Print preset. If the result looks good enough, try Web next time. If you need more detail, step up to Maximum. Keep the original file so you can try again with a different setting.

Expected Compression Ratios by Document Type

Compression results vary significantly depending on what's inside your PDF. Typical ranges depend on the source content, with image-heavy files seeing the largest reductions and already-compressed or text-only files seeing the least:

Document Type	Typical Reduction	Why
Scanned documents	60 to 80%	Raw scans contain uncompressed image data, huge savings when re-encoded as JPEG
Photo-heavy PDFs	40 to 70%	Photos can be re-encoded at lower quality with minimal visible difference
Presentations & slides	30 to 60%	Mix of images, gradients, and text; images compress well, text less so
Office documents (Word, Excel)	20 to 50%	Mostly vector text and simple graphics; less pixel data to optimise
Already-compressed PDFs	5 to 15%	Images are already optimised; re-compression yields diminishing returns

If your PDF contains a mix of content types, expect results somewhere in the middle. The most dramatic improvements come from scanned documents and exported PowerPoint presentations with embedded photos.

Common Use Cases & File Size Limits

Most people compress PDFs because they've hit a file-size wall. Here are the specific limits you're probably dealing with:

Gmail: 25 MB attachment limit. Image-heavy PDFs may fit under this threshold after compression, but results depend on the source file.
Outlook: 20 MB limit (10 MB for some enterprise accounts). Use the Web preset for maximum reduction.
Job portals (LinkedIn, Indeed, Workday): Typically 2 to 5 MB for resume uploads. Compress your portfolio PDF from 15 MB to under 3 MB.
University submissions (Turnitin, Blackboard): Often 10 to 20 MB limits. Particularly relevant for research papers with embedded figures and charts.
Cloud storage optimisation: Compressing archived PDFs can reclaim 40 to 60% of your Google Drive, Dropbox, or OneDrive storage quota.
Website downloads: Smaller PDFs load faster for visitors. A 10 MB product brochure compressed to 3 MB improves page speed scores and reduces bandwidth costs.

Two Approaches to PDF Compression

PDF compression tools broadly fall into two categories, each with different trade-offs:

Approach	How it works	Preserves text?	Typical use case
Lossy rasterisation (this tool)	Each page is rendered as a JPEG image and reassembled into a new PDF	No: text becomes part of the page image	Scanned documents, photo-heavy PDFs, reducing file size for sharing
PDF-aware optimisation (desktop PDF software)	Internal PDF structures are reorganised; images can be resampled without rasterising text or vector elements	Yes: text, form fields, and accessibility tags are preserved	Legal documents, accessible PDFs, forms, portfolios requiring editable text
Upload-based online services	File is sent to a remote server for processing, then returned as a download	Depends on the service and method used	Occasional use where browser-side processing is not available

For everyday compression needs, emailing reports, shrinking scanned documents, and meeting upload limits, browser-side lossy compression can be a practical option. PDF-aware desktop software remains the appropriate choice for workflows requiring selectable text, accessibility tags, form fields, or complex PDF editing.

Privacy and Security: Browser-Side Compression

Many online PDF compressors upload your file to a remote server for processing. That may be acceptable for low-risk documents, but it is worth thinking carefully before sending tax returns, medical records, contracts, or financial statements to an upload service.

This tool works differently. The selected PDF is processed in your browser after the page assets have loaded:

pdf.js (Mozilla's open-source renderer) reads your PDF locally
Canvas API renders each page into a pixel buffer in memory
JPEG encoding happens natively in your browser engine
pdf-lib assembles the final PDF entirely in browser memory

The compression step does not need an upload request for the selected PDF. This reduces exposure compared with upload-based tools, but it is not a substitute for your organisation's rules on confidential, legal, medical, or financial documents.

Batch Compression Tips

This tool supports compressing up to 20 PDFs at once. Here is how to get the most out of batch mode:

Group by quality need: If some files need high quality (portfolios) and others don't (email attachments), compress them in separate batches with different presets.
Use ZIP for 2+ files: When you compress multiple files, the download button automatically creates a ZIP archive, which is easier than downloading files one by one.
Check individual results: After compression, review each file's size reduction. If one file barely shrank, it was likely already compressed, no action needed.
Re-compress with different settings: Not satisfied? Click "Compress Again" to try a different quality level without choosing the files again.
Mind your RAM: Each page is rendered as a canvas. Very large PDFs (200+ pages) may use significant memory. If your browser becomes sluggish, process large files individually.

Troubleshooting Common Issues

"My file got bigger after compression"

This happens when the original PDF is already well-compressed or uses efficient vector graphics. Re-rendering as JPEG images can actually increase file size for text-heavy, already-optimised documents. Solution: try the Web preset, or accept that the file is already as small as it can get with this method.

"Compression is slow on my large file"

Each page is rendered individually using your device's CPU and GPU. A 100-page document means 100 render-and-encode cycles. This is normal, the progress bar shows exactly which page is being processed. Expect roughly 0.5 to 2 seconds per page depending on your device.

"The quality is too low"

Move the slider towards Maximum (95%). At Print quality (70%), some fine detail may be softened. If you need pixel-perfect output, set the slider to 90%+, you'll still see meaningful compression on image-heavy files.

"My text is no longer selectable"

This is expected. The compression method rasterises each page (converts it to an image). If you need selectable text, consider using a PDF-aware compressor that can reduce file size without rasterising. For many sharing and archive copies, rasterised PDFs are usable.

"My PDF shrank but is still too large"

Already-compressed PDFs typically see only 5 to 15% further reduction regardless of preset. If you still need a smaller file, try removing unnecessary pages first using the Organize PDF tool, then compress the trimmed version. For very large documents, splitting into sections, compressing each, and reassembling with Merge PDF can help. Some PDFs simply cannot reach a specific target size with a rasterisation-based approach.

When You Should NOT Compress a PDF

Here are situations where PDF compression isn't the right choice:

Legal or notarised documents: Courts and notaries may require exact digital formatting. Rasterising a legal PDF could invalidate digital signatures or make it inadmissible.
Fillable PDF forms: Compression removes form fields, checkboxes, and interactive elements. The form becomes a flat image.
PDFs with accessibility features: Screen readers rely on tagged text structure. Rasterisation removes these tags, making the document inaccessible.
Already-tiny PDFs: A 200 KB text document won't shrink meaningfully. Compression adds processing time for negligible benefit.
PDFs you need to edit later: Once rasterised, you can't easily edit the text. Keep the original and compress a copy for sharing.

For these scenarios, consider using Organize PDF to remove unnecessary pages, or PDF to Word to extract editable content before compressing.

Related PDF Tools

Organize PDF

Reorder, delete, or rearrange pages to reduce file size by removing unnecessary content.

PDF to Word

Convert PDFs to editable Word documents, extract text before compressing.

Sign PDF

Add signatures to your compressed PDFs, draw, type, or upload your signature.

Image Compressor

Compress standalone images before embedding them in PDFs to reduce the source assets first.

How to use this tool

Upload one or more PDF files

Choose your compression quality level

Click Compress and download your smaller files

Common uses

Emailing large PDF reports that exceed Gmail or Outlook attachment limits
Uploading CVs, resumes, and portfolios to size-restricted job portals
Shrinking scanned documents for cloud storage and archiving
Compressing exported presentation slides before sharing
Reducing PDF size for faster website loading
Compressing invoices and receipts before archiving

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Frequently Asked Questions

How does PDF compression work?

The tool re-renders each PDF page as a JPEG image using your chosen quality level, then reassembles those page images into a new PDF. It is a lossy method, so it can reduce file size but may rasterise text and soften fine detail.

Will compression affect the quality of my PDF?

Yes, it can. The tool renders each page as a JPEG image, so embedded photos, scans, text, and vector graphics are re-encoded together. Fine image detail may soften, and text may no longer be selectable. The Maximum preset keeps more visual detail and minimises visible degradation, while Web prioritises smaller file size.

What compression ratio can I expect?

Results vary based on content. PDFs with many photos or scans typically see 40 to 80% reduction. Office-style documents see 20 to 50%. Already-compressed PDFs see 5 to 15%.

Is it safe to compress PDFs online?

The selected PDF is processed in your browser after the page assets have loaded, and the compression step does not upload the selected file to an iForge Apps server. For confidential, legal, medical, or financial documents, still follow your organisation's handling rules and keep the original file.

Why did my PDF get larger after compression?

This happens when the original PDF is already well-optimised or consists mostly of vector text and graphics. Re-rendering as JPEG images can actually increase file size for such documents. Try the 'Web' preset for maximum reduction, or accept that the file is already as compact as this method allows.

Can I compress password-protected PDFs?

No. Password-protected PDFs are encrypted, and our browser-based tool cannot decrypt them. You'll need to remove the password protection first using your PDF software, then compress the unprotected file.

What's the maximum file size I can compress?

There is no fixed server-side upload limit because compression happens in your browser, but your device memory is the real limit. Large or page-heavy PDFs may slow down or fail, especially on mobile. Process large files one at a time.

Does compression remove metadata from my PDF?

Yes. Because our tool re-renders pages as images and reassembles them into a new PDF, original metadata (author, creation date, keywords) is not carried over. This can be a privacy benefit if you want to strip identifying information before sharing.

Can I compress PDFs on my phone or tablet?

Yes, on modern mobile browsers. Performance depends on your device's memory and processing power, so larger PDFs may take longer or fail on older phones and tablets.

How does this tool differ from desktop PDF software?

Desktop PDF software typically uses PDF-aware optimisation that preserves selectable text, form fields, and accessibility tags while still reducing file size. This tool uses lossy compression by rasterising pages as JPEG images, which can shrink image-heavy files more aggressively but converts text and interactive elements into flat page images.

Does this tool upload my PDF to a server?

No. Compression runs entirely in your browser using pdf.js (Mozilla's open-source renderer), the Canvas API, and pdf-lib. Your file is never sent to an iForge Apps server or any third party. This makes it a practical choice for payslips, bank statements, medical letters, and other documents you would rather not share with an external service. For highly confidential files, follow your organisation's data-handling policy regardless.

What quality setting should I use for emailing a PDF?

Use the Web preset (40%) for maximum reduction when file size is the priority, such as sending a scanned form to a shared inbox. Use Print (70%) when the recipient will read the document on screen and readability matters, such as a report or proposal. Gmail allows attachments up to 25 MB; Outlook allows up to 20 MB (10 MB on some corporate accounts). If your compressed file is still too large, try the Web preset and process the file a second time.

What is the difference between the Web, Print, and Maximum presets?

Web (40%) sets a JPEG quality of roughly 0.49 and a render scale of 1.3, giving the smallest output but softer text. Typical reduction for scanned documents is 60 to 80%. Print (70%) uses roughly 0.72 JPEG quality at 1.7 scale, balancing readability and file size with 40 to 60% typical reduction. Maximum (95%) uses roughly 0.88 quality at 1.9 scale, keeping the most visual detail with 15 to 35% typical reduction. The custom slider lets you fine-tune between any of these points.

How do I compress a CV or portfolio PDF for a job application?

Use the Print preset for a CV or text-heavy portfolio. Job portals such as LinkedIn, Indeed, and Workday typically cap uploads at 2 to 5 MB. A design portfolio with photos usually responds better to the Web preset. Compress the file, check the output size in the results panel, then use Compress Again to adjust the quality if needed. Keep the original file so you can produce a fresh compressed copy at any time.

Can I compress PDFs on iPhone or iPad?

Yes. The tool runs in Safari on iPhone and iPad without any app to install. Larger PDFs may take a little longer because compression uses your device's memory and CPU. For reliable results on mobile, process one file at a time and keep individual files under 20 MB.

My PDF shrank but is still too large. What can I try?

If the file reduced but did not reach your target size, the source PDF is likely already partially compressed or contains content that does not compress much further. Try these steps: switch to the Web preset for maximum reduction; remove unnecessary pages using the Organize PDF tool before compressing; or split the document into smaller sections using Split PDF, compress each section separately, then reassemble with Merge PDF. Already-compressed PDFs typically see only 5 to 15% further reduction regardless of preset.

Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.