How to Compress a PDF to 100 KB or Less (Methods That Work)

To get a PDF under 100 KB, first find out what is inside it. A PDF made from a document (typed text) is usually small already and may need only a light squeeze. A scanned PDF is a stack of photos, and the only way to make it much smaller is to make those photos smaller: export the pages as JPG, shrink each one, and rebuild the PDF with the JPG to PDF converter. With the right settings, one dense A4 page fits in under 100 KB and stays readable.

To be clear about this site's compress PDF tool: it re-saves the file in a tidier structure but does not recompress images, so a scanned PDF barely changes. The rest of this guide shows what does work, with sizes we measured by running the site's own tools in Chrome.

Why some PDFs shrink and scanned ones don't

A text PDF stores letters and the fonts to draw them, which is compact. A scanned PDF stores one picture per page, and the file is roughly the total size of those pictures. Squeezing the structure of the file cannot change much when 99% of it is image data.

Our tests with the compress PDF tool showed exactly that:

So use the compress PDF tool only when a text PDF is a few KB over the limit. For anything scanned, rebuild it.

Not sure which kind you have? Try to select a word in your PDF viewer. If you can, it is a text PDF. If the whole page selects as one block, or the PDF to Text tool reports "No selectable text found", it is a scan.

Rebuild a scanned PDF under 100 KB, step by step

1. Set a budget per page. Take the limit, keep about 3 KB spare, and divide by the number of pages. The rebuilt PDF adds only about 1 KB per page: in our test, one 92.7 KB page image became a 93.6 KB PDF, and three 28.5 KB images became an 87.2 KB PDF. For two pages under 100 KB, aim for about 45 KB each.
2. Export the pages as JPG. Open the PDF to JPG converter, add the PDF and download each page. It draws pages at 144 pixels per inch and high quality, so a dense A4 page came out around 500 KB. That is your starting point, not the final size. (It converts the first 30 pages; split longer files first.)
3. Shrink each page with a fixed width. Open the resize image in KB tool, add one page, choose Custom, type your per-page budget in Maximum size and, this is the key step, type a Width from the table below. Leave height blank so the page keeps its shape. Press Resize image and download. Repeat for each page.
4. Rebuild the PDF. Add the shrunk pages to the JPG to PDF converter in page order (one at a time is the safest way to control the order), convert and download.
5. Check it. Open the new PDF, zoom to 100%, and read the smallest text that matters: a roll number, a date, a seal. Check the size in your file manager before uploading.

Why type a width? Left blank, the KB tool protects picture quality by shrinking the page instead, which suits photos but not documents. For a 45 KB budget it shrank our test page to about 400 px wide, where the body text was barely legible. With the width fixed at 827 px, it kept the page larger and lowered the JPG quality to about 8% instead. The background turned slightly blotchy, but every word stayed readable. For text, size beats smoothness.

What fits under 100, 200 and 500 KB (approximate)

We tested a demanding page: A4, packed with 10.5-point text, a 12-row marks table, a round seal and a signature, with the slightly grey, textured look of a real scan. Pages with less on them come out smaller, so you can often use a bigger width; pages with photos or coloured backgrounds need more room.

The DPI figures assume an A4 page, which is 8.27 inches wide: 827 px is 100 pixels per inch, 1240 px is 150. If the tool says it cannot reach your limit at that width, try the next smaller width. Below about 600 px wide, normal printed text starts to break up, so four or more dense pages in 100 KB is not realistic. Ask whether the portal really needs every page.

Scan smaller in the first place

If you are scanning the paper yourself, you can skip most of that work by choosing sensible settings at the start. This is what our test page weighed as a single JPG at different resolutions (quality 75, a typical scanner default):

• Resolution matters most. Doubling the DPI made the file two to three times bigger. Scan forms and certificates at 150 DPI, or 100 DPI for plain typed text. Use 300 DPI only for small print or if the portal asks.
• A clean background helps a lot. The "document", "whiteboard" or "enhance" filter in phone scanner apps turns the paper pure white. On our page that alone saved 15% at 100 DPI and 37% at 300 DPI, because paper texture is fine detail that JPG has to store.
• Greyscale helps less than you would think. Saving our page in greyscale through the browser saved about 1%, since the page was nearly black and white already. It helps more on coloured paper or when the scanner app saves a true black-and-white file.
• Crop to the page edges so you are not storing the table top around the paper, and scan one page per document side.

If it is a text PDF that is slightly too big

Run it through the compress PDF tool first; it saved 2.5% on our text file, which is sometimes enough. Next, remove pages the portal does not need with the delete pages tool, or keep only the relevant ones with the split PDF tool. Do not convert a text PDF to images unless you have to: a text page of 20–60 KB becomes several hundred KB as a picture.

Uploading to Indian portals: practical points

• KB can mean 1,000 or 1,024 bytes, and portals differ. The KB tool keeps files under the limit in 1,000-byte KB, which passes either way. Windows shows sizes in 1,024-byte KB, so a "98 KB" file there is about 100,350 bytes; stay a few KB below the limit to be safe.
• One PDF or separate uploads? Read the form. If each document has its own upload box, do not combine them; if it asks for "a single PDF", join the shrunk parts with the merge PDF tool. The guide to merging PDF files covers page order.
• Password-protected PDFs, such as many e-statements and the downloaded e-Aadhaar, often fail on portals and give blank pages in this site's PDF tools. Open the file with its password and print it to a new PDF first.
• Keep the original. Make every smaller version from the original scan, not from a copy you already compressed. Each round of JPG compression loses detail, and the next portal may want 50 KB.

For photos and signatures rather than documents, see compressing an image to 20, 50 or 100 KB, and for page images in general, the guide to converting JPG to PDF.

Frequently asked questions

Why did the compress PDF tool hardly change my file?

It only reorganises the file's structure and does not touch images. A scanned PDF is almost all image data, so it stays the same size. Rebuild it from smaller page images instead.

How do I compress a PDF to 100 KB on my phone?

The same steps work in a phone browser: PDF to JPG, then the KB tool with a fixed width for each page, then JPG to PDF. On a phone, process one page at a time and keep the downloads in order.

Can I get a PDF under 50 KB or 20 KB?

Under 50 KB, one dense page fitted at 827 px wide in our test. Under 20 KB is only realistic for a single page with little on it, such as a short letter or an ID card; check carefully that it is still readable.

Will the text be searchable after rebuilding?

No. The pages become pictures. A scanned PDF was not searchable in the first place, so usually nothing is lost.

Is it safe to do this with my documents?

Yes. Each tool in the chain works inside your browser, so the pages never leave your device.

Sources: File sizes measured by running the site's PDF to JPG, resize image in KB, JPG to PDF and compress PDF code in Chrome on a test A4 page and a text PDF, October 2026. Results vary with the page and the browser.