How to scan a document to PDF with your phone

To scan a document to PDF with your phone, lay the page flat under even light, hold the camera parallel to it and fill the frame, capture each page in order, then export the set as a single PDF. Good lighting matters more than any camera setting you can change.

Set up the page before you set up the camera

Almost every bad phone scan is a lighting problem, not a camera problem. Spend ten seconds on the surface and the light and the rest takes care of itself.

• Flatten the page. Press out fold creases, or weight the corners. A curved page produces text that warps at the edges and never straightens out afterwards.
• Use even, indirect light. Daylight near a window, or a room light that is not directly overhead. A single bright lamp close to the page creates a hot spot at one end and shadow at the other.
• Put it on a contrasting surface. A white page on a dark table gives edge detection something to find. White on white is the hardest case for any scanning app.
• Skip the flash. It usually produces a glare patch in the middle of the page, especially on glossy paper.

Hold the camera square to the page

Shoot from directly above the centre of the page, with the phone parallel to the paper rather than tilted. Photographing at an angle makes the page trapezoidal, and while most scanning apps correct that, correction always costs some sharpness.

Your own shadow is the other common problem. If you are leaning over the page, the phone or your head is often between the light and the paper. Stand to the side of the light source instead of with your back to it, and fill the frame with the page so you are not throwing away resolution on the table around it.

How much resolution does a document actually need

For anything you will send to another person, aim for the equivalent of about 300 dpi. That is the long-standing default for document scanning because it keeps ordinary body text and most fine print comfortably readable without producing an enormous file.

Multi-page documents

Capture the pages in order, in one session, and keep the setup identical between shots so the pages do not alternate between bright and dim. Moving the light or changing your distance halfway through is what produces a document where page three looks like it came from somewhere else.

Keep the whole thing as one file. A single PDF with the pages in order is far easier for a recipient to handle than five separate images, and it is also much harder for a page to go missing on the way.

The usual problems, and what fixes them

• Glare patch. Move the light or the page rather than the phone, and turn off the flash. Glossy paper may need light from a shallow angle.
• Shadow across the page. Reposition yourself relative to the light source, or hold the phone slightly off to the side and correct the perspective afterwards.
• Blurry text. Tap to focus on the text before capturing, and brace your elbows. Low light makes the camera use a slower shutter, which is where handshake shows up.
• Skewed edges. Recapture from directly overhead. It is quicker than fighting the crop.
• Strange patterning. If you are photographing a screen rather than paper, the interference between the screen's pixels and the camera sensor causes it. Ask for the file instead.

Then fill it in and send it

A scan is usually not the destination — the form still needs completing. In FormFill you tap Scan to capture a paper form with your camera, tap anywhere on the page to add text, checkmarks, X marks or the date, drop your signature, and tap Done to flatten it into a clean PDF saved to your library and ready to share.

Everything happens on the device. There is no account and no cloud backend, so the scan of your passport or your lease never gets uploaded anywhere in the process.