How to scan documents with your phone into one PDF under 100 or 200 KB

Portals often want a certificate, an ID card front and back, or a mark sheet as one PDF of 100 or 200 KB. A phone camera is a perfectly good scanner if the photos are taken with that goal in mind, and the size limit is easy once the pages are clean.

Taking the photos

• Lay the page flat on a dark, plain surface so its edges are easy to see and crop.
• Use even daylight or overhead light; turn the flash off. Glare on glossy paper hides text.
• Hold the phone straight above the page, not at an angle, and fill the frame with the paper.
• One photo per page, in order. Check each one is sharp before moving on.

Crop away everything that is not paper

Desk, fingers and shadow cost bytes and make the page look like a photo of a page. Crop each image to the paper edges with the crop tool before building the PDF. On a 100 KB budget this alone can be the difference between readable text and mush.

Colour or black and white

Document mode turns each page into clean black and white: it estimates the paper colour across the page, so a photo that is darker on one side still comes out white, and stores the result as 2-bit or, when the limit is tight, 1-bit grey. Text stays sharp at a fraction of the size. In our tests, three phone photos of printed pages fitted 200 KB at full resolution this way, where colour JPEG had to shrink and blur them.

Keep colour when the colour carries meaning: a photograph on an ID card, a coloured stamp or seal, a signature in blue ink that must look blue. In colour mode the tool lowers JPEG quality before it lowers resolution, so text stays legible as long as possible.

Building the PDF

• Add the pages, then drag rows or use the arrow buttons to set the order.
• Choose A4 (or Letter) with small margins for documents; 'fit to image' when the page size should match the photo.
• Turn on the size limit and enter the portal's figure, for example 100 KB.
• Create the PDF and check the size and page count in the result row before downloading.

What fits in a size limit