Compress a PDF to 100 KB, 200 KB, 500 KB or 1 MB: What Is Realistic

Application portals love small limits. 100 KB for a certificate, 200 KB for a CV, 500 KB for an email attachment, 1 MB for an assignment. Whether your PDF can meet one of them depends less on the tool than on what is inside the file, so it helps to know what is realistic before you start.

Why some PDFs are tiny and others are huge

A PDF made from typed text stores letters as text and fonts, which compresses very well. A one-page typed document is often between 20 and 80 KB. A scanned page is different: it is a picture of a page. A picture needs a value for every pixel, and a scan at reading quality has millions of them.

Here is how many pixels an A4 page holds at common scan resolutions:

A page scanned at 300 dpi holds about 40 times as many pixels as the same page at 48 dpi. This is why lowering the resolution is by far the most effective way to shrink a scan, and why a colour phone photo of a document can weigh megabytes while the text on it would fit in a few kilobytes.

How the tool reaches a target

The size pages (100 KB, 200 KB, 500 KB and 1 MB) all use the same method as the main Compress PDF tool in its target-size mode, and the order is deliberate:

1. Lossless repack. The file is rewritten more efficiently without touching its content. If this is already under the limit, you are done and the text stays selectable.
2. Stepped image quality. If not, each page is redrawn as a compressed image, trying 150, 110, 96, 72, 60 and 48 dpi in turn, each with a lower JPEG quality than the one before.
3. First fit wins. It stops at the first step where the file is under your limit, so you get the best-looking result that fits, not the smallest possible one.

If even the lowest step cannot reach the limit, the tool says so and gives you the smallest result instead of pretending. It handles up to 20 files at once, files up to 150 MB, and redrawing works on PDFs of up to 200 pages.

What fits under each limit

These are rules of thumb for scanned pages. They are not guarantees, because a clean black-and-white page compresses much better than a page with a photo or a coloured background.

• 100 KB: typed documents of a few pages, or one or two scanned pages at 72 to 96 dpi. A multi-page scan is unlikely to fit and stay readable.
• 200 KB: two or three scanned pages at about 96 to 110 dpi, or a short typed document with a logo.
• 500 KB: roughly four to eight scanned pages at 96 to 110 dpi, or a designed document with a few images.
• 1 MB: a longer scan or a report with screenshots, usually with a light touch.

A rough scale is that a screen-readable scanned page commonly takes between 60 and 150 KB, depending on the content. Divide the limit by that range to estimate how many pages fit.

Make the file easier to shrink

The biggest gains come before compression.

• Scan in grayscale or black and white, not colour.
• Scan at 150 dpi, not 600. Anything above about 200 dpi adds size without helping a screen reader.
• Crop the dark borders and the empty margins. They carry no information and cost bytes.
• Remove pages you do not need with Split PDF, then compress. Every page you drop leaves room for the others.
• If a portal accepts several files, compress each separately instead of merging first.

Check the result before you upload

Open the compressed file and zoom to 100 percent. Read the smallest print: names, dates and numbers. If the image steps were needed, the pages are now pictures, so the text cannot be selected or searched. Keep your original for copying.

Privacy

All of this happens inside your browser. The PDF is not uploaded, which matters for certificates, identity documents and contracts. For the wider picture on file size, see how to reduce PDF file size without losing quality.