How to scan a document with your phone properly
Someone has asked you for a scan of a document, and you do not own a scanner. You photograph it, send it, and a day later you get the reply: we cannot read this, please send a proper scan.
Almost every time this happens it is one of four things, and all four are about the physical setup rather than the app. Get those right and a phone produces a scan that is genuinely indistinguishable from a flatbed one for text documents.
Put the page on something that contrasts with it
This is the one people get wrong most often, and it is the one that breaks automatic edge detection completely.
A scanner app finds the document by looking for the boundary between the page and whatever is behind it. A white page on a white table has no boundary. A white page on a pale wooden desk has a weak one. The app then either crops the wrong rectangle, or gives up and hands you the whole photo including your table.
Put white paper on something dark. A dark table, a closed laptop, a folded dark jumper, the floor if the floor is not pale. The improvement is immediate and larger than anything else on this list.
The corollary matters too: if you are scanning something dark or printed edge-to-edge, put it on something light.
Get your own shadow out of the frame
You are standing over the page with a light source somewhere behind or above you. Your head and your phone will cast a shadow directly onto the thing you are photographing.
The fix is to light the page from the side rather than from behind you. A window to your left or right beats a window in front of you. A room light off to one side beats a ceiling light you are standing directly underneath.
Avoid using the flash where you can. It produces a bright hotspot in the middle and dark corners, and on glossy paper it produces a white blob that removes whatever text was underneath it. Even lighting from a window is better than any phone flash.
Hold the phone square to the page
Photograph a rectangle from an angle and you get a trapezoid. Scanner apps correct for this — that is what the perspective correction is doing when it straightens the crop — but correction stretches pixels, and past about twenty degrees the text at the far edge visibly smears.
Hold the phone flat above the page, parallel to it, centred. If you find yourself leaning to avoid your own shadow, move the page rather than the phone.
Two practical helpers: rest your elbows on the table to steady the shot, and if the document is larger than A4, step back and use the full frame rather than getting close and shooting at an angle.
Check the result before you send it
The last one is not a technique, it is a habit, and it is the difference between one round trip and three.
Open the finished PDF and read it. Not skim it — actually read a line of the small print. If there is a signature, look at the signature. If there is a reference number, check you can distinguish an 8 from a 6. Rescanning one page now takes fifteen seconds; discovering on Monday that the bank could not read your payslip costs you a week.
Why they asked for a PDF and not a photo
If the request specifically said PDF, there are real reasons behind it, and they are not bureaucratic fussiness.
- Page order and count. A twelve-page document as twelve separate images arrives in whatever order the mail client felt like. As one PDF it is unambiguous, and the recipient can tell at a glance that nothing is missing.
- Orientation. Photos carry rotation metadata that different systems interpret differently. A page that looks upright on your phone can arrive sideways in someone’s document viewer. A PDF fixes the orientation into the file.
- Boundaries. A photo of a document includes your table, your hand, and the edge of your laptop. A scan is the page, cropped to the page.
- Size. A set of full-resolution photos is often too large for the upload limit on the form they are asking you to use, and a text-document PDF is usually far smaller.
A repeatable setup worth keeping
If you scan things more than occasionally, spend two minutes finding a spot and then reuse it. A dark surface near a window, with the light coming across rather than from behind you. Once you know the spot works, scanning stops being a small project each time.
For multi-page documents, keep the pages in a stack face down beside you and move each one to the same position after shooting it. Keeping the position constant means the crop is consistent, and keeping the stack ordered means the pages are too.
A note on privacy
The documents people scan are, disproportionately, the sensitive ones: passports, payslips, tenancy agreements, medical letters. It is worth knowing where the file goes after you have made it.
Many scanning apps process on a server, which means an image of your ID leaves your phone. That is not necessarily wrong — plenty of reputable services do it, and features like text recognition are easier that way. But it is a thing worth choosing deliberately rather than discovering, and it is worth being deliberate about the copy that stays in your camera roll afterwards, syncing to whatever else is signed into that account.
Where the app fits
Document Scanner does the mechanical part of the above: it finds the page edges automatically, straightens and crops to them, stacks multiple pages into one document in order, and exports a PDF. Scans are saved into folders inside the app rather than into your camera roll, and can be locked behind Face ID.
Processing happens entirely on the device — nothing is uploaded and nothing is shared with a third-party service. The honest trade-off is that there is no cloud backup either, so export anything you need to keep.
If you also need to merge, reorder, annotate or sign the resulting file, that is a different job — PDF Go is built for it.
Document Scanner
Automatic edge detection, multi-page PDFs, Face ID locking, and nothing leaves your iPhone.
