Compress a PDF for an upload limit without making it unreadable

Why you’d do this

Almost every portal that accepts a PDF also caps it — a visa application, a bank’s document upload, a government e-service, a university admissions form. The limit is usually somewhere between 2 MB and 10 MB, and the file you actually have is very often bigger than that, especially if it came from a phone camera or a scanner app that didn’t think about file size at all.

The annoying part is that “just compress it” can go wrong in the other direction: squeeze too hard and a scanned ID or a contract page turns into a blurry, half-legible mess that gets rejected for a different reason. What you actually want is the smallest file that’s still clearly readable, and a way to check that before you hand it over.

How, with the named tool

Dzzz’s Compress PDF tool does the shrinking; Document Scanner is there if your starting point is a photo rather than an existing PDF.

1. Add your PDFs. Drop them on the box or tap to choose — you can add several at once and remove any of them with the × button.
2. Pick a quality preset. Choose Smallest (Screen), Balanced (Ebook) or High quality (Print). Balanced is selected by default.
3. Download the engine once. The first time you use the tool, tap “Download engine (~12 MB · one time)” — that’s Ghostscript, the program doing the actual compression, running in your browser. Once your device has it, the button turns into Compress and you’re never asked again on that device.
4. Compress and save. Tap Compress, watch the percentage, then save each result from its own button, or take everything at once as a ZIP. If a PDF is already about as compressed as it’s going to get, the tool says so directly and offers to keep the original instead of a barely-smaller copy.

If what you’re uploading started as a photo — a paper form, a receipt, an ID card — Document Scanner turns it into a clean PDF first: photograph or upload the page, drag the four corners onto the page edges, pick a look (Colour, Greyscale, Black & white or Auto), and export as a PDF. That PDF is often already small because a scanned, flattened page compresses better than a raw camera photo — but it can still go through Compress PDF afterward if the portal’s limit is tight.

What to watch for

The three presets trade detail for size, and text stays sharp longer than images do. Screen throws away the most — it’s built for reading on a monitor, not printing — Print keeps the most, and Balanced/Ebook sits between the two. Ghostscript compresses the PDF’s embedded images (photos, scanned pages, logos); ordinary typed text stays crisp at every preset, which is why Screen is often fine for a mostly-text contract but too rough for a document that’s essentially a photograph of an ID or a signature.

A PDF you scanned is all image, so it compresses differently than one you typed. Document Scanner’s PDF has no selectable text — every page is stored as an image — so it responds to the presets the same way a photo would: Screen can visibly soften small print or a signature. If a scanned page needs to survive compression and stay legible, try Balanced first and only drop to Screen if you’re still over the limit.

Compress PDF never hands you back a bigger file. If Ghostscript’s output would end up larger than what you started with — which can happen on a PDF that’s already efficiently encoded — the tool keeps your original instead of delivering a “compressed” file that’s actually bigger.

Check the result before you upload it, not after it’s rejected. Open the compressed PDF and look at the pages that matter most — a photo ID, a signature, small print — at the zoom level a reviewer might actually use. The size-before-and-after number the tool shows you says nothing about whether a signature is still legible; only looking at it does.

Password-protected PDFs are rejected outright. Remove the password first, in whatever tool put it there, then compress.

FAQ

Which preset should I start with for a government upload?

Balanced (Ebook) — it’s the tool’s own default and a reasonable first try for most scanned forms and text documents. Drop to Screen only if you’re still over the portal’s limit and the pages that matter are still readable at that setting; check them before you upload.

Will compressing a PDF make a signature or stamp illegible?

It can, at the more aggressive presets, because those are usually small image details and Screen compresses embedded images the hardest. Zoom into that specific area of the compressed PDF before uploading — don’t rely on the overall size number to tell you whether a small detail survived.

My PDF barely got smaller — is something wrong?

No — some PDFs are already close to as compressed as Ghostscript can get them, especially ones that started as text rather than scanned images. The tool tells you directly when that’s the case and offers to keep your original rather than replace it with a copy that isn’t meaningfully smaller.