Which settings in a scanner app give the smallest PDF?

Greyscale, 150 DPI, and a crop tight to the sheet. Those three choices bring a one-page scan to roughly 150KB to 400KB before any compression, which this page then takes under 100KB with little visible change. Colour at 300 DPI starts five to ten times heavier and shows it in the result.

The result says my pages were saved as pictures. Is the certificate still usable?

It still prints at the same size, and the scan was a picture anyway, so nothing that could be selected has been lost. What matters is legibility: zoom into the preview and check the name, the certificate number and the date of issue. If any of them is unclear, rescan at a lower resolution so the file starts smaller, or reduce the page count.

Can I put two certificates into one 100KB PDF?

Merge them first with the merge tool, then bring the combined file here. Two greyscale pages usually survive at 100KB with readable print; two colour pages are pushed into the picture stage. If the portal has a separate field per document, upload them separately and give each one the whole limit.

Is 100KB enough for a colour scan?

For one page, yes, with some grain in the coloured areas. The compressor searches for the highest JPEG quality that fits rather than guessing, so the photo on an ID card remains recognisable. Beyond one colour page the budget is spread too thin, and greyscale scanning is the better route.

Compress PDF to 100KB for Certificate and ID Scans

One hundred kilobytes is the figure most often attached to a single document: one caste certificate, one ID proof, one domicile letter, each in its own upload field. Many Indian recruitment portals ask for scanned certificates as PDF with limits between 100KB and 1MB, and the 100KB end of that range is the one that bounces the most uploads, because a phone scan of one page is twenty or thirty times heavier.

The 100KB figure is already in the size box, so all that is needed is the file. A one-page greyscale scan nearly always lands here with its photographs re-compressed and nothing else altered. A multi-page scan is a different story, and the notes below describe what it turns into and how to scan so that it does not come to that.

A university degree certificate with a red seal and two signatures

How to use it

Add the PDF the portal refused, straight from the scanner app or a downloaded copy.
The tool repacks the file, then lowers the quality of the scanned page until it fits under 100KB.
Read the stage named on the result card and open the preview to make sure the certificate number is still legible.
Download the file and upload it to the same field.

What a single page looks like at 100KB

A 150 DPI greyscale scan of an A4 page runs to about 150KB to 400KB as a JPEG, so a one-page certificate needs its quality lowered a little, or the picture reduced slightly, and that is all the second stage does to it. Printed text, the registrar’s signature and the office stamp stay readable, and the page keeps its 210 × 297 mm size. A colour scan of the same page starts at 1MB to 3MB at 300 DPI and has much further to fall, so expect visible JPEG grain in coloured areas such as a photograph or a hologram sticker.

Why two or more scanned pages go soft

Two scanned pages share the same 100KB, and three share it again. At some point no JPEG quality setting gets the embedded scans small enough, and the third stage takes over: each page is rendered afresh and the PDF is rebuilt from those pictures at whatever resolution fits. For a three-page scan that is a low resolution, and the result card reads pages saved as pictures. Names stay readable; small print such as a serial number may not. If the field accepts only one document, consider whether every page is really required before shrinking all of them.

Scanning so the file is small to begin with

Most of the weight in a scanner-app PDF is decided before this page sees it. Scan in greyscale rather than colour unless a colour photo or stamp is being verified; set the app to 150 DPI rather than 300; and crop to the paper’s edges, since the desk around the document costs as many bytes as the document itself. A page scanned that way is often already near 100KB and loses almost nothing here. Leave the colour-enhancement filters off, because they add noise that JPEG then pays for on every pixel.

Frequently asked questions

Which settings in a scanner app give the smallest PDF?: Greyscale, 150 DPI, and a crop tight to the sheet. Those three choices bring a one-page scan to roughly 150KB to 400KB before any compression, which this page then takes under 100KB with little visible change. Colour at 300 DPI starts five to ten times heavier and shows it in the result.
The result says my pages were saved as pictures. Is the certificate still usable?: It still prints at the same size, and the scan was a picture anyway, so nothing that could be selected has been lost. What matters is legibility: zoom into the preview and check the name, the certificate number and the date of issue. If any of them is unclear, rescan at a lower resolution so the file starts smaller, or reduce the page count.
Can I put two certificates into one 100KB PDF?: Merge them first with the merge tool, then bring the combined file here. Two greyscale pages usually survive at 100KB with readable print; two colour pages are pushed into the picture stage. If the portal has a separate field per document, upload them separately and give each one the whole limit.
Is 100KB enough for a colour scan?: For one page, yes, with some grain in the coloured areas. The compressor searches for the highest JPEG quality that fits rather than guessing, so the photo on an ID card remains recognisable. Beyond one colour page the budget is spread too thin, and greyscale scanning is the better route.