Compress PDF

How to compress a PDF

1. Choose or drop the PDF. Compression starts at once; the counter shows which image or page is being worked on.
2. Pick the method. Keep text shrinks only the photos and scans inside the file, so the text stays sharp and searchable. Maximum turns every page into a compressed picture, which makes the smallest files but means the text can no longer be selected.
3. Pick how strongly. Recommended (150 DPI) suits screens, email and most upload portals; Smallest file (96 DPI) is for reading on a screen only; High quality (220 DPI) keeps photos good enough to print. If a form or mailbox sets a limit, choose Under a file size and the limit — 100 KB to 10 MB — and the tool picks the best quality that fits.
4. Download the compressed PDF. The result shows the new size and how much smaller it is. If no setting makes the file smaller, you're told why, and nothing worse than your original is offered.

What makes a PDF large — and what can be compressed

A PDF holds text (as characters plus the fonts to draw them), vector drawings, and images. Text and drawings are tiny and already stored compressed; a 50-page report of plain text is often well under 1 MB. What makes PDFs big is almost always images: a phone photo of 4,000 × 3,000 pixels, a page scanned at 600 DPI, or a picture pasted into a document at full camera resolution. On a printed page such an image is shown a few inches wide, so most of its pixels are never seen.

That is where compression works. Each photo is reduced to at most as many pixels as a full page at the chosen resolution — 1,275 × 1,650 pixels for a US Letter page at 150 DPI — and saved again as a JPG at a lower quality. Images that are already smaller, or that come out no smaller, are left exactly as they were.

Keep text or Maximum?

Keep text edits the file in place. Only images change; text, fonts, vector drawings, links, bookmarks, form fields and the page layout stay byte for byte as they were. It also removes data no viewer shows — earlier versions of an edited file that are still stored inside it, page thumbnails, and the private editing copy of the artwork that Adobe Illustrator saves into its PDFs — and packs the document's small internal objects together so they compress better.

Maximum draws every page as a JPG image at the chosen resolution and builds a new PDF from those pictures. It is the way to shrink a PDF whose size doesn't come from photos — huge embedded fonts, extremely detailed drawings, maps — and it gives the most predictable size per page. The price: the text becomes part of the picture, so it can't be selected, searched or read aloud by a screen reader, links stop working, and form fields are flattened. Use it for documents that are only meant to be looked at, such as signed scans.

Worked example

We tested the tool on a 3-page report of 11.4 MB: a 4,000 × 3,000 pixel photo saved as a high-quality JPG, a 1,600 × 1,200 pixel PNG with a transparent area, and two 1,500 × 1,000 pixel images stored losslessly, each shown about 7 inches wide, plus headings in ordinary text. These are the measured results:

With Keep text the headings stayed selectable in every case, and the pages looked the same as the original at normal zoom. The photo went from 4,000 × 3,000 to 1,650 × 1,238 pixels at 150 DPI — still more than the roughly 1,070 pixels it actually covers on the page. By contrast, a 12-page text-only document of 16.5 kB couldn't be made smaller: the tool kept the original, and Maximum would have turned it into 3.4 MB of page pictures. A PDF whose content streams were saved uncompressed, on the other hand, went from 159 kB to 16 kB with the text unchanged.

Your PDF stays on your device

Most "compress PDF" websites upload the file to their servers, process it there and promise to delete it later. The PDFs people compress are typically the ones they need to send somewhere: tax returns, pay slips, bank statements, contracts, medical reports, ID scans for an application. Here the PDF libraries are loaded into your browser and do all the work on your own computer or phone, so the file is never sent anywhere.

Limits

• Text-only PDFs barely shrink. If a file has no photos, there is little to remove without turning the text into pictures; the tool says so and keeps your original.
• Some images are left alone because re-encoding them could change their colors or break them: CMYK images from print workflows, images with limited palettes, 16-bit images, JPEG 2000, and black-and-white fax-style scans (JBIG2, CCITT), which are already very compact. Small images such as logos and icons are skipped too.
• Protected PDFs (a password or a lock against changes) can't be compressed. Open the file in your PDF reader, enter the password if asked, print it to a new PDF ("Save as PDF" or "Microsoft Print to PDF") and compress that copy.
• Digital signatures are invalidated by any change to the file, compression included. Compress before signing, or keep the signed original.
• Large files are held in your device's memory; a computer is more reliable than a phone for PDFs over 100 MB.

To make a PDF smaller by removing pages instead, use Delete Pages from PDF or Split PDF. For single photos, the image compressor and Reduce Image Size in KB give finer control, and JPG to PDF turns compressed photos into a PDF.

Frequently asked questions

Last updated: October 15, 2026