Compress PDF

PDF compression reduces a document's file size so it is faster to email, quicker to upload, and lighter to store, without changing what is printed on each page. The need comes up constantly: an email provider rejecting a 20 MB attachment, a government portal capping uploads at 5 MB, or a company shared drive that fills up because every scanned contract is stored at full resolution.

This tool compresses PDFs entirely inside your browser rather than on a remote server. It reads the PDF's internal structure with the pdf-lib library and rewrites it in a more compact form, then hands you the smaller file to download — your document is never uploaded anywhere. That makes it a reasonable option for people who want to shrink a PDF quickly without sending contracts, tax documents, or medical records to a third-party server.

It is worth setting expectations correctly: browser-based PDF compression is genuinely more limited than what a dedicated desktop tool like Adobe Acrobat can do, because deep image recompression and font subsetting are heavier operations. This tool works best on PDFs that have redundant internal structure (common with files re-saved multiple times or exported from certain office software) and will do little to a PDF that is already tightly optimized.

Many email systems block attachments over 20-25 MB, and government or university portals often cap uploads far lower, sometimes at 1 MB or even a few hundred kilobytes. Whether a PDF can actually reach that target depends almost entirely on what is inside it: a text-only contract of a few pages is often already under 200 KB, while a 20-page scanned document full of high-resolution photos might start at 15 MB and be difficult to bring under 1 MB without reducing image quality.

If your file does not shrink enough after compression, the biggest lever is usually the scan resolution or embedded photos, not the PDF wrapper itself. Scanning documents at 150-200 DPI instead of 300-600 DPI before creating the PDF in the first place produces a dramatically smaller starting file, which is often more effective than compressing an already-scanned high-resolution PDF after the fact.

• A 300 DPI scanned page can be 3-5x larger than the same page at 150 DPI
• Text-based PDFs (not scanned images) compress far more predictably
• Removing unused embedded fonts or unnecessary pages reduces size before compression even runs

Lossless compression rewrites the file more efficiently without discarding any visual information — every pixel and character stays exactly as sharp as before, but redundant internal data is stripped out. This tool performs a lossless-style structural cleanup: it rebuilds the PDF's internal object structure with pdf-lib, which can shrink files that carry duplicate or bloated internal objects, while leaving the actual images and text completely untouched.

Lossy compression, by contrast, actually re-encodes embedded images at a lower quality or resolution, which is how tools achieve the largest size reductions (sometimes 60-80%) on image-heavy PDFs, at the cost of some visible quality loss if pushed too far. Because this tool does not re-encode images, savings on scanned or photo-heavy PDFs will typically be smaller than what a lossy image-recompression tool can achieve.

It is normal to compress a PDF and see little to no size reduction, or occasionally a file that is a few bytes larger than the original. This happens when the source PDF was already saved efficiently — for example, by Adobe Acrobat, a modern printer driver, or another compression tool — leaving little redundant structure left to remove. A PDF that has already been compressed once will rarely shrink much further with a second lossless pass.

The files most likely to see a meaningful reduction are older PDFs, PDFs re-saved many times by different editing tools, and PDFs created by combining multiple documents (such as a merged file), since these often accumulate duplicate fonts, images, or metadata that a structural rewrite can clean up.

If a PDF is large mainly because of embedded photos and this tool's structural compression does not bring it down enough, a more effective approach is to reduce the size of the images before they go into the PDF at all. Exporting scanned pages as JPEG at 70-80% quality, or resizing photos to the resolution actually needed for on-screen or standard printing (150-300 DPI), then rebuilding the PDF, usually produces a smaller final file than compressing the finished PDF after the fact.

For PDFs made up mostly of standalone images rather than mixed documents, it can be faster to extract the images, compress them individually with an image compressor, and reassemble the PDF, rather than relying on PDF-level compression alone.

Because this tool processes the file entirely in your browser and never transmits it to a server, there is no upload step where a confidential contract, tax return, or medical record could be intercepted or stored remotely. This is a meaningfully different privacy model from web tools that require uploading your file to a server for processing, and it is one of the main reasons to choose a browser-based compressor for sensitive documents.

The tradeoff is processing power: since your own device does the work instead of a server farm, very large files (over roughly 50-100 MB) can be slower to process or use more memory than they would on a dedicated server-side compression service.