Guide

Compress PDF without losing too much quality

Updated September 2026 · Shrink the file for email or a portal without turning type into mush or photos into blotches.

Most “compress PDF” buttons aim at the smallest file, not the file you can still read. If your real limit is “small enough to upload,” stop at the first setting that clears that bar. For a broader size-and-readability checklist, use Compress PDF without wrecking readability. This page is the quality-preserving path: milder image settings, fewer rasterize-everything tricks, and a hard stop when the page looks worse than the original.

Quality-first compression

Decide what “good enough” means before you touch a slider:

• Screen / email. Body text should look crisp at 100% zoom on a laptop. Photos can lose fine grain.
• Print a form. Thin table rules and small numbers matter more than photo detail.
• Photo-heavy scan. Faces, stamps, and handwriting need more pixels than a typed letter.

If you are already under the size limit, do not compress. Extra passes only add generation loss, especially when the PDF already contains JPEG photos.

What actually damages quality

• Re-JPEGing photos. Each “medium quality” pass adds blockiness around edges. Run one pass from the original, not three from yesterday’s compressed copy.
• Downsampling text scans too far. A black-and-white letter can often go to about 150–200 dpi for email. Going to 72 dpi makes stems of letters collapse.
• Printing the PDF to a new PDF. Convenient on Windows, but it may turn sharp vector type into a page-sized image. Search dies; zoom looks soft.
• Maximum / low / “email (smallest)” presets. Those labels optimize for kilobytes. Start at a middle preset and only go harsher if you still miss the limit.
• Converting to Word and back. That is an editing path, not a quality path. See the PDF to Word checklist.

Settings that stay gentle

Exact menu names differ by app. Look for optimize / reduce file size / export, then:

• Color photos: downsample toward 150 dpi for screen, 200–300 dpi if someone might print the photo.
• Black-and-white text: downsample less aggressively than color; bicubic or “retain text quality” if the app offers it.
• JPEG quality: start around a high or medium-high setting, not minimum. Numbers like “80” vs “40” (when shown) are a starting point, not a universal rule — judge the page.
• Leave fonts embedded. Subsetting is usually fine; converting text to outlines or images is not.
• Do not flatten unless you must. Flattening comments or layers can rasterize markup you still needed.

Online tools that offer only one unnamed slider are guessing. Use them only on non-sensitive files, pick the milder end, and inspect the download. There is no honest “tiny file, identical quality, unlimited free” mode.

A safer sequence

1. Copy the original. Work only on the copy.
2. Drop pages you do not need. A 30-page scan of a 6-page form is not a quality problem. Delete or extract or split first.
3. If one page is a huge photo appendix, extract it. Compress the text packet mildly; keep the photo page at a higher setting or send it separately.
4. Run one optimize/export pass at a middle preset. Note the new size.
5. If you are still over the limit, try a slightly stronger image downsample — still from the original copy, not from pass one.
6. If you are far over, rescan at a sensible resolution or split the packet. Crushing a 600 dpi phone-scan packet will always look worse than scanning once at 200–300 dpi.

On a Mac, Preview’s export quality slider is a reasonable first try for image-heavy files. On Windows, prefer a PDF app’s optimize command over Print to PDF when you care about sharp type. After either path, open the new file in a different viewer than the one that created it if you can — that catches “it looked fine in the exporter’s preview.”

How to judge the result

Do this at 100% and at 200% zoom, not in a thumbnail strip:

• Letters have smooth edges, not gray halos or missing holes in e, a, 8.
• Tables: rules still meet; footnotes still read.
• Signatures and stamps: strokes are continuous, not a checkerboard.
• Photos: no obvious 8×8 JPEG blocks on faces or sky unless you accepted that trade.
• Search still finds a word you know is in the original (if the original had real text).
• Page size and rotation match. A “compressed” file that also shrank the crop is a different bug.

Fail any of those and export again from the original with milder settings. Two readable files beat one ugly file. If you later need a picture of a page, export that page as an image with the PDF to JPG/PNG guide instead of screenshotting a crushed preview.