Application forms often ask for certificates, mark sheets, caste or income certificates and ID proofs as PDFs with a tight cap. TNPSC's resize notice, for example, gives 200 KB for supporting documents. Then the scanner app produces a 3 MB file for a single page. The size is decided almost entirely at the moment of scanning, so this guide is about the settings, with the fix for files you already have at the end.

What decides the size of a scanned PDF

A scanned PDF is basically a JPEG of each page wrapped in a PDF. Its size depends on four things:

  1. Resolution. A page scanned at 600 DPI has four times the pixels of one at 300 DPI, and sixteen times those of 150 DPI. For a document a person reads on screen, 150–200 DPI is plenty.
  2. Colour mode. Colour stores three channels; greyscale stores one. A typed certificate in greyscale is usually far smaller and just as readable. Keep colour only where the stamp or seal colour matters, and check what your form says.
  3. Number of pages. Each page adds its own image. If the form asks for one page, don't include a blank back side.
  4. Compression quality. Scanner apps often default to "best". Medium quality is invisible on text.

Scanning with a phone

  • Use a document scanning mode (Google Drive's scan on Android, or the "Scan Documents" option in Apple's Notes app). It flattens the perspective, crops the page and whitens the background, which also makes the file much smaller.
  • Choose black-and-white or greyscale for typed documents.
  • Place the page on a dark, plain surface so the edges are detected cleanly.
  • Scan in daylight. Shadows and yellow indoor light become grey areas that cost bytes.

Scanning with a flatbed or office scanner

  • Set 150 or 200 DPI instead of the default 300 or 600.
  • Choose greyscale for text documents.
  • Save as PDF with "medium" or "web" quality if the software offers it.
  • Scan each document separately so you can attach the right one to each slot.

Rough targets

As a rule of thumb, a clean one-page A4 document in greyscale at 150 DPI is usually well under 200 KB. A colour photo-ID card scanned on an A4 bed, with the rest of the page left white, is mostly white space, so crop to the card first. The exact numbers depend on the paper, so check the result before you upload.

Fixing a PDF that is already too big

  • Compress it to a target: the PDF compressor re-renders each page at a lower resolution and quality until it fits the KB you type. It runs in your browser, so the certificate is not uploaded.
  • Start again from images: if you have photos of the pages, the image to PDF tool builds one PDF under a size limit from them.
  • Remove pages the form does not ask for.

Re-rendering turns any selectable text into an image of text. For upload forms this does not matter; officers read the page, they do not search it.

Check that it is still readable

Open the compressed PDF and zoom to 100%. Your name, roll number, marks, dates and the stamp must all be legible. A document that is under the limit but unreadable can be rejected at verification, which is worse than a failed upload.