A 30 MB PDF that your email refuses to send, or a phone that keeps running out of space — the problem is rarely the document itself. Most PDFs carry high-resolution images and stored data nobody needs. Handled correctly, you can cut more than half the size without anyone noticing a difference.

This guide explains what makes a PDF heavy, how to pick the right compression level, and when compressing actually hurts the file.

First: know which kind of PDF you have

There are two very different types of PDF, and they behave differently under compression.

File type What is inside What compression affects Typical saving
Text PDF (exported from Word or Google Docs) Real text + embedded images Images only 5% – 25%
Scanned PDF (scanner or phone photo) One large image per page Image resolution 50% – 85%
Image PDF (catalog, deck) High-resolution photography Image quality 40% – 70%

Rule of thumb: the more a file depends on images, the more compression helps. The more it depends on text, the smaller the gain — text was never the heavy part.

The workflow: compress in 4 steps

  1. Open the Compress PDF tool.
  2. Drag your file in, or pick it from your device.
  3. Choose a compression level — this is the decision that matters.
  4. Press Compress PDF Now, compare the before/after size, then download.
Always keep the original. If the result is not good enough, try another level from the original instead of compressing the compressed file.

Choosing the right level

1. Light — best for text documents

Light compresses the file without rasterising pages, so text stays real text: sharp, selectable and searchable. Savings are modest (5–25%), but quality is pixel-identical.

Use it for: contracts, CVs, reports, anything you will print or send to an official body.

2. Medium — the balanced default

Each page is rendered as a high-quality JPEG. Savings are large (50–85% on scans) while text stays clearly readable on screen and in normal printing.

Use it for: scanned documents, WhatsApp and Telegram sharing, archiving, and files you will not need to search inside.

3. High — when size is the only priority

Smallest file, lowest quality. Fine for very large documents that must fit a hard upload limit, but avoid it for small text or important numbers — detail degrades visibly when zoomed.

6 things that save more than compression

  • Delete unneeded pages first. Every removed page saves space before you start — use Split PDF.
  • Merge first, compress once. Merging strips duplicated fonts and structures — use Merge PDF, then compress the single result.
  • Downscale images before embedding them. A 4000 px photo shown at 8 cm is wasted weight.
  • Convert to JPG if you do not need the text. PDF to JPG plus image compression often wins.
  • Scan at a sane resolution. 600 dpi instead of 300 doubles the size for no visible gain.
  • Strip metadata. Camera data, software strings and unused fonts add weight and nothing else.

Common mistakes

  • Compressing the same file repeatedly. Each pass loses more quality.
  • Using High on a small text document. You lose clarity for no real saving.
  • Using apps that upload your files. A privacy risk, usually with a watermark.
  • Judging by file size alone. Open the result and zoom to 200% before deleting the original.
  • Compressing a password-protected PDF. Some tools fail or strip the protection — unlock it first if it is yours.

Bottom line

There is no single "best" compression. The rule is: text file → Light, scan or images → Medium, and High only when forced. Always compare against the original before you delete it.

Try it now: compress your PDFs for free in the browser.