How to Reduce PDF Size to Under 100 KB, 200 KB or 1 MB for Online Upload

Oct 24, 2026 · 3 min read · Documents

Certificates, mark sheets, caste certificates and ID cards usually need to be uploaded as PDFs, often with a tight limit such as 100 KB, 200 KB or 1 MB. A PDF made by a phone scanner app can easily be 3 to 10 MB. Here is how to bring it down without making it unreadable.

Why scanned PDFs are so big

A scanned PDF is really a set of photos, one per page, wrapped in a PDF file. The size depends on how many pages there are, how many pixels each page photo has, and how much detail is kept. Scanner apps often save every page at very high resolution, which is far more than a website needs to read a certificate.

Method 1: compress the PDF

1. Open Compress PDF and add your file.
2. Choose Strong mode. It redraws each page as a JPG, which gives the biggest saving for scans.
3. Type the portal's limit (for example 200) in Target size, or start with the High level. The result shows the old and new size.
4. If it is still too big, try the Extreme level or Strong mode. Open the result and zoom in to check you can still read every word.

Strong mode makes the text non-selectable, which does not matter for a scanned certificate. For a PDF made from Word with real text, use Recommended mode, since it keeps the text sharp.

Method 2: build the PDF from compressed photos

For very tight limits such as 100 KB, you get more control by starting from photos:

1. Take a clear photo of each page in daylight, straight from above.
2. Open the image compressor, set Max width to about 1000 pixels and Target size (KB) to your limit divided by the number of pages, minus a little. For a two-page document under 200 KB, use about 90 KB per page.
3. Download the pages, then add them in order to JPG to PDF and download the PDF.

Quick size guide

• One page under 100 KB: about 1000 pixels wide at medium quality is usually readable.
• One page under 200 KB: about 1400 pixels wide gives clear text.
• Several pages under 1 MB: the High level usually fits five to ten pages.

Other ways to save space

• Remove pages you do not need with Delete PDF pages. Blank backs of pages add size for nothing.
• Crop the edges of each photo before making the PDF. A table top around the paper is wasted space.
• Use black and white for text documents. Many scanner apps have a document mode that makes the paper pure white, which compresses much better.
• Split it if the portal allows several files: Split PDF lets you upload each part separately.

Check before you upload

Open the final PDF on your phone, zoom in on the smallest text such as a roll number or seal, and make sure it is readable. A file that fits the limit but cannot be read can still get your application rejected.

Frequently asked questions