Compress a PDF to under 100 KB.

• UPSC, signature, three in one image (JPEG): File size: 20 KB – 100 KB. Image dimensions: 350 - 500 pixels. (UPSC, instructions for uploading the photo and signature)
• IBPS, handwritten declaration (JPEG): File size: 50 KB – 100 KB. (IBPS CRP PO/MT-XVI notification, pp. 39–42)

Like 50 KB, a 100 KB limit is more often on an image than on a PDF: UPSC's and IBPS's are JPEGs, which the photo and signature resizer makes with the right pixels too. Use this page when a portal asks for a PDF under 100 KB, which is typically a single-page declaration, undertaking or ID.

• One page comes out clear: in our test a dense A4 page of small type made 96 KB without the tool having to drop below 120 DPI, so a marksheet's fine print stays readable.
• Two dense pages fit at 72 DPI (96 KB in the same test), where small print goes soft but a normal letter reads fine. Three or more typed pages won't fit; split the file.
• Grey pages help most on colour scans of black-and-white documents: same legibility, fewer bytes.
• The check counts 1,000 bytes to the KB, the stricter reading, so a portal counting 1,024 accepts the same file.

Every page is redrawn as a JPEG at the sharpest DPI that fits, from 200 down to 72, so the file is only as small as it has to be. The tool tells you the DPI it settled on when it goes below 120.

• Scan at 150 DPI in greyscale rather than 300 DPI in colour; the tool can only shrink what it's given, and a lighter start ends smaller.
• Crop the page to the document. A card photographed on a table carries the table in every byte.
• If it must be several pages, split them into one PDF each and upload separately where the portal allows.
• If a page is mostly a photograph, no PDF trick helps: a photo needs bytes. Ask whether a JPEG is accepted instead.

Photos of documents rather than a PDF? The images-to-PDF tool makes one PDF under the same limits, and an Aadhaar goes through the safe Aadhaar copy tool, which masks the number as well.