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How to Compress a PDF to Under 100 KB, 500 KB, 1 MB or 2 MB for an Upload Limit

Portals cap uploads at arbitrary sizes. Find out what is making your PDF big, then follow a recipe for each common limit — with the settings that keep it readable.

7 min read

The upload form says 2 MB. Your PDF is 9 MB. Now what?

Job portals, visa applications, university admissions, tax offices, tender systems and insurance claims all cap the size of a PDF you can upload — commonly 100 KB for a photo-sized document, 500 KB or 1 MB for a form, 2 MB or 5 MB for a scanned bundle. The cap is arbitrary and the error message is unhelpful. The fix depends entirely on what is making the file big, so this guide starts there, then gives a step-by-step recipe for each common limit. Every tool mentioned runs in your browser; the document is never uploaded anywhere while you shrink it.

First: find out why the file is big

Open the PDF and try to select a word with the cursor. That single test tells you which of the two worlds you are in:

What happensWhat the PDF containsWhat compression can do
Text highlights word by wordReal text plus fonts; images only where there are picturesText pages are already tiny (a few KB). Size comes from embedded images, fonts or leftovers — target those.
Nothing selects; the page is one pictureA scan or a photo — every page is an imageSize is pixels × quality. Lowering resolution and JPEG quality shrinks it 5–20×.

A 20-page contract exported from Word is usually 200–600 KB. The same contract scanned at 300 dpi in colour is 20–40 MB. If your file is far larger than its page count suggests, something inside it — photos, a scanned signature page, an embedded font family, a leftover high-resolution logo — is the culprit, and the recipes below deal with each.

The main lever: rasterized compression

Compress PDF on this site re-renders every page as a JPEG at a resolution and quality you choose and rebuilds the document from those images. It is blunt but predictable: the output size is almost exactly pages × (pixels per page × quality factor), so you can hit a target by turning two dials.

SettingTypical A4 pageLooks likeUse for
150 dpi · quality 0.8150–300 KBCrisp on screen, fine to printGeneral documents, 2–5 MB limits
110 dpi · quality 0.770–120 KBReadable, slightly soft1 MB limits on 5–10 page files
96 dpi · quality 0.640–70 KBScreen-only, small text softens500 KB limits
72 dpi · quality 0.520–40 KBThumbnail-grade; body text still legible100–200 KB limits on 1–3 pages

The trade-off is that text becomes pixels: it is no longer selectable or searchable. For a document that only needs to be read and filed, that is fine. For one that must stay searchable, use the structural options in the next section first and only rasterize if they are not enough.

Structural options that keep text as text

  • Compact PDF rewrites the file, dropping unused objects, old revisions left behind by editors and duplicate resources. Files that were edited many times often shrink 20–50% with no visible change at all. Try this first — it never hurts.
  • Remove PDF Metadata strips XMP packets and embedded thumbnails; usually only a few kilobytes, but on a tiny limit every kilobyte counts.
  • Grayscale PDF removes colour. Scans of black-and-white paper are typically 40–60% smaller in greyscale at the same resolution.
  • Extract Images from PDF shows you what pictures are embedded and at what size. A 2,000-pixel logo on a page that displays it at 100 pixels is pure waste; shrink the image with the Image Resizer and rebuild the page with Image to PDF, or accept the rasterized route.
  • Split PDF or Extract PDF Pages when the form only needs some pages. Uploading the three relevant pages of a forty-page statement is both smaller and kinder to the reviewer.

Recipes for the common limits

LimitTypical documentRecipe
100 KBOne-page ID, certificate or signature pageExtract the one page → Grayscale if the original is monochrome → Compress at 72–96 dpi, quality 0.5–0.6. Crop white margins first with Crop PDF if the scan has them; margins cost pixels.
500 KB2–5 page form or letterCompact PDF → if still over, Compress at 96–110 dpi, quality 0.6–0.7.
1 MB5–10 page applicationCompact → Grayscale (if scanned) → Compress at 110 dpi, quality 0.7.
2 MBScanned bundle of 10–20 pagesGrayscale → Compress at 120–150 dpi, quality 0.7–0.8. Check that stamps and small print survive.
5 MBLong report with photosCompact first; often enough. Otherwise Compress at 150 dpi, quality 0.8 — photos stay acceptable.

Work from the gentlest step down. After each tool, look at the size shown next to the download button; stop as soon as you are under the limit with a little headroom, because some portals measure size after their own re-encoding and reject files sitting exactly at the cap.

Check the result before you upload

  • Open the output and zoom to 100%. Small print, stamps, handwritten dates and signatures must still be legible — those are what a reviewer looks for.
  • Count the pages. Compression tools never drop pages, but a wrong Extract range does.
  • If the portal requires searchable text (some tax and court systems do), do not rasterize. Use Compact, page extraction and image resizing only.
  • Keep the original. Compression is one-way; a rasterized file cannot be restored to text.

When nothing gets it small enough

A 300-page scan will not fit in 2 MB at any legible quality — that is roughly 7 KB per page, below what a readable page needs. In that situation the honest options are to split the document into several uploads (many portals allow multiple attachments), to ask whether the system accepts a ZIP (ZIP Create does not shrink JPEG pages much, but some caps are per-file rather than per-total), or to contact the organisation and explain. Uploading an unreadable file to satisfy a size cap usually just delays the request when a human opens it.

Frequently asked questions

Why did the file get bigger after compressing?

The original was mostly text (a few KB per page) and rasterizing turned each page into an image (tens of KB). For text documents use Compact PDF and image resizing instead of rasterized compression.

Can I compress a password-protected PDF?

Not directly — the pages are encrypted. Unlock it first with Unlock PDF (you need the password), compress, then protect the result again if required.

Which dpi should I use for a document that will be printed?

150 dpi is the floor for print; 200 is safer for small text. Below that, printed text looks jagged even though it reads fine on screen.

Does the site keep my compressed file?

No. Compression runs in your browser with PDF.js and pdf-lib; nothing is uploaded, and the result exists only as the download you save.

Will compressing remove the signature or form fields?

Rasterized compression flattens everything into the page image — signatures stay visible, but form fields stop being fillable. Compact PDF keeps fields intact.

How do I compress many PDFs to the same limit?

Run each through Compress PDF with the same settings; results scale with page count, so files with more pages need a lower dpi.

Tools mentioned in this guide