Compress a PDF: Which Setting Actually Shrinks It

A compressor offers a quality level, a resolution and a few housekeeping switches, and the results can differ by an order of magnitude. Knowing which control does the work saves a second and third pass.

Why this comes up

A scan of twenty photographed pages and a text-only report do not respond to the same settings. One is mostly pixels and shrinks readily; the other is mostly text and barely moves.

Check before you run it

• Lower the image resolution before touching the quality level. The ppi box sets how many pixels per inch the images are kept at. A 300 ppi scan dropped to 144 ppi loses more weight than a move from Best to Medium, and the page still reads on screen.
• Use the quality level to protect fine detail. Medium is the sensible first pass, while Good and Best keep more detail in photographs and thin lines. Text stays text at every level, so a text-only file will not shrink much whichever you choose.
• Read the result honestly. Multimedia files are discarded by default and fonts are optimised; both help a file that carries attachments or unused faces. If the download is the same size as the upload, the compressor found nothing worth removing, not a reason to lower quality again.

When to reach for it

• A scan-heavy file has to fit an upload limit. Drop the resolution to the smallest value that still reads, then check a dense page at 100% before sending.
• A text-only report is still too large. Check for embedded images, attachments and unused fonts before compressing harder; the text itself is not where the weight is.

One question we get

Will compression hurt the quality?

Pick the level: Extreme shrinks most, Recommended balances both, Low preserves fine detail. The size inspector shows the exact result before you commit.

Where it fits

The tools people usually open next to Compress:

• Flatten — Makes fillable PDFs read-only. Print & scan in one step
• Repair — Recover data from a corrupted or damaged PDF document
• Watermark — Add an image or text watermark to PDF documents.

Every tool works on a copy, so the original file is never touched. Uploads are stored under an unguessable id and deleted automatically two hours after you last open them; nothing is listed, shared or indexed. More on the security page.