How to scan documents to PDF with your phone

By Grace Whitfield, office-operations consultant · Updated November 1, 2026

You no longer need a scanner to send a signed form, a receipt or a school document as a PDF. A phone camera is sharper than most office scanners — the difference is in how you take the photo and what happens to it afterwards. This guide covers both: how to shoot a page so it scans cleanly, and how to turn the photos into one tidy PDF for free.

Set up the shot

Use contrast: light paper on a dark surface

Automatic edge detection — in FormFlow and in other scanner apps — works by finding the light rectangle of paper against a darker background. A wooden table, a dark folder or a coloured countertop is ideal. White paper on a white desk is the hardest case; if that is all you have, you can drag the four corners into place yourself.

Light it evenly, without flash

Daylight from a window, or a ceiling light behind you, is best. The phone's flash makes a bright hotspot and a glare on glossy paper. Watch for your own shadow: holding the phone directly above the page often puts the shadow of your hand and phone on the paper. Step to the side so the light comes from beside you.

Get all four corners in the frame

Leave a little background showing on every side. A slight angle is fine — FormFlow straightens it — but a page photographed at a steep angle loses sharpness at the far edge. Hold the phone roughly parallel to the paper.

Flatten the page

Folded letters and curled receipts produce wavy lines that no app can fully straighten. Press folded pages flat under a book for a minute before you shoot.

Turn the photos into a PDF with FormFlow

1. Open Scan to PDF on your phone and tap Take a photo. Your camera opens. Or tap Choose photos to pick existing pictures — several at once if you have a multi-page document.
2. FormFlow finds the edges of each page and shows four round handles. If a corner is off, drag it onto the corner of the paper. Whole photo keeps the full image; Rotate turns a sideways page.
3. Choose a look: Black & white for text documents (sharpest, smallest file), Auto colour for documents with colour logos, stamps or highlighter, Grayscale for photos or pencil.
4. Add more pages with Photo or Add pages, and reorder them with the arrows.
5. Pick the page size — US Letter for most US paperwork — and tick Make text searchable if you want to search the PDF later.
6. Tap Create PDF, then Download. The photos never leave your phone; here is how that works.

What happens to the photo

It is worth knowing why a "scan" looks better than the original photo:

• Perspective correction. The four corners are mapped back to a true rectangle, so lines that converged in the photo become parallel again.
• Adaptive black & white. Instead of one brightness cut-off for the whole page, each pixel is compared with its neighbourhood. That keeps text black even inside a shadow, and turns a grey background white.
• Sensible size. A 12-megapixel photo is reduced to about 2,000 pixels on its long side and compressed, which keeps text crisp while making a typical page a few hundred kilobytes instead of several megabytes.

Other options worth knowing

Your phone may already have a scanner: on iPhone, the Notes app and the Files app have a "Scan Documents" option, and Google Drive on Android has a scan button. They are good choices. Use FormFlow when you want to choose the filter and page size, add searchable text, or go straight on to signing or filling in the scanned document — the result screen hands the PDF over to the next tool without downloading it first.

Common problems

• The crop grabbed the table, not the page. The background was too light. Drag the corners, or reshoot on a darker surface.
• Text looks broken in Black & white. The photo was blurry or very dark. Try Grayscale, or retake it with more light and a steadier hand.
• "This browser cannot open HEIC photos." Some browsers outside Safari do not decode iPhone HEIC files. Use the camera button on the page, or set the iPhone camera to Most Compatible in Settings › Camera › Formats.