Plenty of government job portals, university admission sites, and exam application forms in India and elsewhere cap PDF uploads at 100KB. If your scanned certificate or filled form is larger, the upload gets rejected. Here is how to get a PDF reliably under 100KB without installing anything and without sending your documents to a server.
Why 100KB specifically?
Many older government and exam portals were built around tight storage budgets, so they enforce small per-file limits — 100KB is one of the most common. The limit usually applies to scanned documents like photos, signatures, mark sheets, and ID proofs.
Because these documents are images, they compress well: reducing the image resolution and JPEG quality shrinks the file dramatically while keeping it readable.
The quickest way (in your browser)
Use a target-size compressor that lets you pick 100KB directly. Drop your PDF in, choose the 100KB target, and download the result. A good tool downsamples the embedded images progressively until it hits the target, while leaving any real text selectable.
The advantage of a browser-based tool is privacy: your certificate or ID never leaves your device. That matters for documents containing personal information.
Tips to hit 100KB without it looking bad
Scan or export at a sensible resolution to begin with — 150 DPI is plenty for most forms; 600 DPI scans are needlessly huge.
If a colour scan won't shrink enough, a grayscale version is much smaller and is usually accepted for documents.
If a single page still won't fit, check whether the portal accepts the document split across the allowed size, or whether a slightly higher limit (like 200KB) applies to that field.
What if it can't reach 100KB?
A long, multi-page, image-heavy PDF may not compress to 100KB without becoming unreadable. In that case, reduce the page count (upload only the required page), scan in grayscale, or lower the source resolution before exporting to PDF.
A pure-text PDF is a different story — it may already be small, and forcing it smaller offers little benefit.