You scanned a form, the portal says "maximum file size 1 MB", and your PDF is 6 MB. This happens all the time with job applications, visa and university portals, bank forms and email attachments. The fix takes a minute once you know what is making the file big.
Why some PDFs are huge
Almost all of a large PDF's size comes from pictures. A PDF made from a Word document is mostly text and stays small. A PDF made from a phone scan or a camera photo holds one large photo per page, often 3,000 pixels or more across, which is far more detail than a form needs.
- Scanned pages and phone photos: usually 1–3 MB per page. These shrink the most.
- PDFs with embedded photos (brochures, reports): large because of the images inside.
- Text-only PDFs (exported from Word or Google Docs): usually already small; compression saves little.
Two ways to compress, and which to choose
Strong compression (best for scans)
Each page is redrawn as a compressed image at a sensible resolution. A 6 MB scan of a two-page form usually drops to a few hundred KB. The trade-off: the text becomes part of the picture, so you can't select or search it. For forms and certificates, that rarely matters.
Basic compression (keeps text selectable)
The file's internal structure is repacked without changing how anything looks. Text stays sharp and searchable. Savings are smaller, often 5–30%, and sometimes the file is already as tight as it can be.
Step by step: get a PDF under a size limit
- Open the Compress PDF tool and drop in your file. It is processed in your browser, so it is never uploaded.
- For a scan or photo PDF, choose Strong and Medium, 110 dpi. For a document with real text, try Basic first.
- Press Compress PDF. The result shows the old and new size before you download.
- Still too big? Run it again at Low, 72 dpi or with a lower image quality.
Which settings hit which size
These are typical results for a scanned A4 page. Your files will differ, so check the size shown after compressing.
| Target | Setting to try | Readability |
|---|---|---|
| Under 1 MB (2–5 pages) | Strong, 110 dpi, quality 70 | Clear on screen and in print |
| Under 500 KB | Strong, 110 dpi, quality 55 | Clear on screen |
| Under 200 KB (1–2 pages) | Strong, 72 dpi, quality 50 | Readable; small print gets soft |
Other tricks when the limit is very small
- Remove pages you don't need. Blank backs of scanned pages double the size for nothing. Use Remove pages first.
- Split it. If the portal allows several uploads, split the PDF into parts.
- Scan in greyscale. If you can re-scan, black-and-white or greyscale pages are much smaller than colour.
- Start from photos. If you only have phone photos, make the PDF with JPG to PDF, then compress it.
Frequently asked questions
Does compressing a PDF reduce quality?
Strong compression lowers image detail, which you can see if you zoom far in, but forms and documents stay readable at normal size. Basic compression doesn't change how the pages look at all.
Is it safe to compress a PDF with personal documents online?
Only if the file isn't uploaded. ToolPeasy's Compress PDF works inside your browser, so passports, payslips and contracts never leave your device.
Why did my PDF not get smaller?
It was probably already efficient, such as a text PDF exported from Word. Basic compression can't shrink it much; if it has images, try Strong.