What actually makes a PDF big
Most PDFs are big for one reason: pictures. A phone photo of a certificate, a scanner set to 300 DPI in colour, a report with a photo on every page. The text in a PDF is tiny by comparison. A ten-page contract typed in Word is often under 100 KB, while one photographed page can be 2 MB.
So this tool shrinks the pictures and leaves everything else alone. Text, lines, tables and signatures drawn as vectors are never turned into an image, which is why they stay sharp, selectable and searchable after compressing. Then a lossless pass packs the file’s structure tighter, which helps a little on every PDF and is the only thing we can do for one with no photos in it.
Light, Balanced or Strong
| Setting | Photos and scans become | Good for |
|---|---|---|
| Light | up to 220 DPI, high JPEG quality | printing, or when it only needs to be a bit smaller |
| Balanced | about 150 DPI | email, WhatsApp, most upload forms |
| Strong | about 100 DPI | the smallest file that still reads well on screen |
If you’re not sure, keep Balanced. At 150 DPI a scanned page still prints cleanly on A4 and looks the same on a phone or laptop screen. Strong is for when you need it smaller still and nobody will print it.
When a form gives you a size limit
Job portals, exam forms, visa and passport sites and bank KYC uploads often say “PDF, max 200 KB” or similar. Pick Exact size, type the number and press the button. We try the quality settings from sharpest to smallest and keep the sharpest version that fits.
There are pages that start on the most common limits: 20 KB, 50 KB, 100 KB, 200 KB, 500 KB and 1 MB. Each one shows what fit under that size in our own tests.
We count 200 KB as 200,000 bytes. Some sites count 204,800. Using the smaller number means the file gets through either way.
How small can a scanned page go?
We ran the size pages on real phone photos and scans of certificates, letters and statements. For a page that is a photo or a scan, roughly:
| Per page | You get |
|---|---|
| about 30 KB | the smallest that stays readable, rough edges |
| 45 to 70 KB | readable, small print a little soft |
| about 90 KB | clean, clear text |
| about 170 KB | sharp |
| 440 KB or more | close to the original |
That gives you a quick way to guess before you start. Five scanned pages need about 450 KB to look clean. Ten pages fit under 1 MB at clear quality. A single photographed page will not get under 20 KB without turning to mush, and we’ll say so rather than hand you an unreadable file.
PDFs made from Word, Excel or a website are a different story. Their text costs almost nothing, so they can go much lower than scans.
On an iPhone or Android phone
It works in Safari and Chrome on the phone, with no app. Tap Choose file, pick the PDF from Files (iPhone) or Downloads (Android), then press Compress. The file is handled by the phone itself, which is also why it’s quick: there is no upload and no download from a server, only the save at the end.
When it doesn’t get smaller
A few PDFs barely shrink, and the result screen tells you why:
- It’s already well compressed. Someone, or the scanner app, has already done this. Making it smaller still would mean visibly worse photos, so we keep yours.
- It has no photos or scans. We pack its structure tighter, and that’s all there is to gain. Big fonts embedded in the file are the usual cause, and we leave fonts alone so the text stays exactly right.
If you need it under a limit and it won’t go, Split PDF by size can cut it into parts that each fit, or Delete PDF pages can remove the pages the form doesn’t need.
Checked against the tool on 22 October 2026. How we write and test these guides