How to scan a document properly with your phone

Organisations reject phone scans constantly, and almost never because the phone was not good enough. It is a shadow across the page, a corner cut off, or an angle that turned the page into a trapezium.

Your phone camera comfortably out-resolves a flatbed scanner. What it does not do automatically is control lighting, hold the page flat, or square up the frame — and those three things are the whole difference between a document and a snapshot of one.

Getting the capture right

• Use indirect daylight. Overhead light puts your own shadow across the page; direct sun blows out the white and loses faint print.
• Shoot straight down. A page photographed at an angle comes out as a trapezium, and no amount of processing fully undoes it.
• Fill the frame but leave a margin. Cropping tight is how corners go missing, and a missing corner is a rejected document.
• Put the page on a dark surface, which makes the edges unmistakable.
• Hold still. Blur is the one fault nothing recovers from — brace your elbows if you have to.

If the document is stapled or folded, deal with that before you shoot. A curled page catches light unevenly down the fold and no processing evens it out.

Why it has to be a PDF

One file rather than six attachments, in a fixed page order, that opens the same way on every device and prints predictably. Most organisations asking for a scanned document will not accept a folder of photographs, and many upload forms accept nothing but PDF. Scan to PDF assembles your captures into one document in the order you set.

It is still a picture of text

A scan contains no text — it contains an image that looks like text. It cannot be searched, and nothing can be copied out of it. That is fine for submitting a form and frustrating a year later when you are trying to find one statement among two hundred. PDF to Text will tell you in seconds whether a given file has real text in it.

Size, and why scans are enormous

A photograph of a page at full phone resolution is several megabytes, and ten pages will not go through email. Compress PDF typically takes 70 to 90 percent off a scanned document, because phones capture far more detail than anyone reading the page will ever use. There is more on why scans get so large if you want the detail.

Everything here happens on your device. The documents people scan most often — passports, bank letters, tenancy agreements — are precisely the ones that should not be uploaded anywhere to be turned into a PDF.

Common questions

How many pages can I scan into one PDF?

As many as your device's memory allows, which in practice is a great many. Very long documents are easier to handle in batches of twenty or so.

Do I need a scanner app?

No. The capture is the camera you already have; the assembly into a PDF happens in your browser.

Why was my scan rejected?

In order of frequency: a corner or edge cut off, a shadow across the text, glare on a laminated document, or the file being too large to upload. All four are capture problems rather than phone problems.