You finish a document, try to attach it to an email, and get the message: file too large. Or a job portal, university form or government website refuses your PDF because it’s over the size limit. This is one of the most common PDF problems, and it’s usually easy to fix.

Why some PDFs are so big

A PDF that contains only text is tiny. A 20-page report written in Word and saved as PDF is often under 500 KB. PDFs get heavy because of what’s inside them:

  • Scanned pages. A scanner or phone camera turns every page into a large photo. Ten scanned pages can easily reach 10–30 MB.
  • High-resolution photos. Pictures pasted from a modern phone camera are often 3–5 MB each, even when they appear small on the page.
  • Embedded fonts and extra data. Some design programs store full font files, editing history and hidden layers inside the PDF.

Common size limits you’ll run into

Gmail lets you attach up to 25 MB per email, but many work and university email systems stop at 10 or 20 MB. Online application forms are often stricter, with limits of 1, 2 or 5 MB per document. Check the limit before you start, so you know how much you need to shrink the file.

How to compress a PDF for free

  1. Open the Compress PDF tool.
  2. Drag your PDF onto the page, or tap Choose file.
  3. Pick a compression level: Light keeps the best quality, Recommended suits most documents, and Strong gives the smallest file.
  4. Click Compress PDF and download the result. The tool shows the old and new size so you can check it fits your limit.

The whole process happens in your browser, so your document is never uploaded anywhere. That matters for bank statements, ID cards and contracts.

Which compression level should you choose?

Start with Recommended. Open the result and zoom in on the smallest text. If it’s still sharp, you’re done. If the file is still too large, try Strong. That level works well for documents people will read on screen, but it may look soft if printed. If the document will be printed or contains fine detail like signatures or stamps, use Light.

One thing to know: compression saves each page as an optimized image. That’s what shrinks scans and photos so dramatically, but it also means the text in the compressed copy can no longer be selected or searched. Keep your original file if you’ll need to copy text from it later.

More ways to make a PDF smaller

  • Remove pages you don’t need. Blank pages, cover sheets and duplicate scans add weight. Use Remove Pages before compressing.
  • Split one big file into parts. If a form allows several uploads, Split PDF can break a large document into smaller sections.
  • Shrink photos before you make the PDF. If you’re building a PDF from phone pictures, run them through Compress Image first, then combine them with JPG to PDF.
  • Scan at a lower resolution. For text documents, 150–200 DPI is enough. 600 DPI scans are much larger and rarely needed.

Quick checklist

  • Know the size limit you’re aiming for.
  • Delete pages you don’t need.
  • Compress on Recommended, then check the smallest text.
  • Keep the original in case you need selectable text later.