PDF Compressor

About the PDF Compressor

Most large PDFs are large because of the pictures inside them: scans, phone photos and screenshots saved at high quality and at a resolution far beyond what the page needs. This compressor finds those images, re-encodes them as JPEG at the quality you choose and, where they are much sharper than necessary, reduces their resolution. Text, fonts and vector drawings are left exactly as they are, so the text stays sharp, selectable and searchable.

Before you start, the tool shows what the file is made of, so you know whether compression can help. Afterwards it shows the real before-and-after size and a side-by-side preview. If the result is not smaller, it says so and you keep your original. Everything happens in your browser; the PDF is never uploaded.

Common uses

• Getting a scanned application, statement or certificate under an upload limit on a government, bank or job portal.
• Emailing a report or brochure full of photos without hitting attachment limits.
• Shrinking phone-camera scans of receipts and documents before archiving them.
• Cleaning up PDFs that grew after repeated edits, which leave unused objects behind.

Which method should I use?

• Compress images (best for most files) re-encodes photos and scans as JPEG and lowers their resolution when they are much sharper than needed. The page layout, text and vector graphics do not change.
• Optimise structure is lossless: it removes unused objects, merges duplicate images and embedded font files, recompresses data streams more tightly and packs the document structure into compressed object streams. Nothing visible changes, but the savings are usually small.
• Maximum turns every page into one JPEG image and rebuilds the PDF. It gives the smallest files for scanned documents, but the text can no longer be selected, copied or searched, and links, bookmarks and form fields are lost. Use it only when size matters more than everything else.

What is left untouched, and why

Some images cannot be re-encoded safely in a browser, so they are kept exactly as they are: CMYK images from print workflows (converting them would change their colours), masks and transparency layers, images in unusual colour spaces, and image formats such as JBIG2 or JPEG 2000. Black-and-white scans stored with fax-style (CCITT) or JBIG2 compression are already very compact. Small images are skipped too, because there is little to gain.

A re-encoded image is only used when it is clearly smaller than the original, and the tool never lowers the resolution of an image unless it knows how large it is drawn on every page that uses it. When most of a file is images the tool cannot re-encode, it says so before you start.

Why some PDFs hardly get smaller

PDFs created directly from Word, Excel or a web page are mostly text, fonts and vector graphics, which are already stored compactly. Fonts must stay embedded to keep the text looking right. For such files, expect a few percent at most — the tool will tell you honestly when there is nothing worth saving.

Limitations

• Encrypted or password-protected PDFs are not supported, because rewriting them would remove or break their protection.
• Any change to a digitally signed PDF invalidates the signature; the tool warns you when a file is signed.
• Files marked as PDF/A (archival) are still valid PDFs after compression, but may no longer pass a PDF/A check.
• The whole document is processed in memory, so files are limited to 200 MB and very large files can be slow on phones.
• The first use downloads the PDF engines once (about 0.75 MB compressed), so it needs an internet connection.

Privacy

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.