How to Scan Documents to PDF with Your Phone (Clean, Readable Scans)

Most of us have sent a “scan” that was really a slightly tilted photo of a page on a kitchen table, complete with a thumb in the corner and a yellow cast from the ceiling light. It works, technically. But the person on the other end has to zoom, squint and rotate, and an upload portal may reject it outright because the file is 9 MB.

The good news is that a modern phone camera is better than most office scanners were ten years ago. What makes the difference is not the hardware. It is the few seconds of setup before you press the shutter, and what happens to the photo afterwards.

What a good scan actually looks like

Before getting into technique, it helps to know what you are aiming for. A scan that nobody will complain about has five qualities:

• Straight edges. The page is a rectangle, not a trapezoid, and there is no table or carpet around it.
• White paper. The background is clean white or very light grey, not beige, blue or patchy.
• Sharp text. You can read the smallest print at normal zoom, including stamps and handwriting.
• Sensible size. Usually a few hundred kilobytes per page, not several megabytes.
• Correct order. Page 1 is first, nothing is upside down and nothing is missing.

Everything below is about hitting those five points with as little fuss as possible.

Before you take the photo

Thirty seconds of preparation saves more time than any filter can. These are the things that matter, roughly in order of impact.

Put the page on a darker surface

Edge detection works by finding where the white page ends. A white sheet on a white desk gives it almost nothing to work with. A wooden table, a dark folder, a coloured cloth or even a pair of jeans makes the outline obvious, and the crop comes out right first time.

Use even light, ideally daylight

A spot near a window during the day is hard to beat. Overhead room lights tend to throw your own shadow (and the phone’s) across the page. If you must use the flash, avoid glossy paper: the flash leaves a bright patch exactly where the text is.

Flatten the paper

Folds and curls turn into grey shadows and wavy lines. Press the page flat with your free hand at the edge, or put something heavy along the top margin. For a booklet or a book, scan one page at a time and press near the spine.

Hold the phone flat and fill the frame

Hold the phone parallel to the page, directly above it, close enough that the page fills most of the screen but with all four corners visible. A small angle is fine because the page is straightened afterwards, but steep angles make the far edge of the text softer.

Wipe the lens

It sounds trivial. It is also the most common reason for a hazy scan. Phone lenses live in pockets and collect fingerprints.

Scanning step by step with Scan to PDF

You don’t need to install a scanner app. CleanPDF’s Scan to PDF runs in the phone’s browser, and the photos are processed on the phone itself, which matters when you are scanning a passport page or a medical report.

1. Take the photo.

   Tap Take a photo. On a phone the camera opens; on a laptop a webcam view appears. You can also choose photos you took earlier.

2. Check the crop.

   The page edges are found automatically and the page is flattened even if you shot at an angle. If a corner landed on the table instead of the paper, drag it to the real corner and tap Done.

3. Pick a filter.

   Magic evens out light and shadow and makes the paper white while keeping colours. More on choosing filters below.

4. Add the other pages.

   Tap Add page for each page. Drag pages to reorder them, and rotate or delete any page that went wrong.

5. Create the PDF.

   Choose A4, US Letter or the photo’s own size, pick a quality level and tap Create PDF. The file is saved to your phone, ready to email or upload.

Choosing the right filter

The filter decides how the page looks and has a big effect on file size. There is no single best option; it depends on what is on the paper.

You can set one filter for all pages and then change a single page. That is handy for a contract where every page is plain text except the last one, which has a coloured stamp and a blue signature.

Getting the file size right

A photo straight out of a phone camera is often several megabytes. Ten of those in a PDF and you are past most email limits. The scanner already shrinks pages a lot, and the Quality setting does the rest:

• Smaller file for upload forms, job portals and anything with a size limit.
• Good for email and everyday sharing.
• Best when someone will print the document or zoom into fine detail.

If a portal has a hard limit such as 100 KB or 1 MB and the PDF is still over, run it through a compressor with a target size, for example Compress PDF to 100 KB or Compress PDF to 1 MB. Black & white pages compress far better than colour ones, so that is the first thing to switch if you are fighting a limit.

Getting the text out of a scan

A scan is a picture of text. You can read it, but your computer can’t search it or copy from it. If you need the words themselves, to paste into an email or edit a paragraph, run the PDF through PDF to Text (OCR). Recognition works best on exactly the kind of scan described above: flat, sharp, evenly lit and straight. A clean scan is the biggest single thing you can do for OCR accuracy.

Tricky documents

Long receipts

Photograph them in two or three overlapping sections and add each as a page. Thermal paper fades quickly, so use Grayscale and scan receipts soon after you get them.

ID cards and small cards

Put the card on a dark surface and fill the frame with it. Scan the front and the back as two pages, use the Original filter so colours are preserved, and choose “Same as photo” as the page size if you don’t want the card sitting in the middle of an empty A4 page.

Books and bound reports

The curve near the spine is the enemy. Scan one page at a time, press the page flat, and keep the phone above the centre of the page rather than the spine.

Whiteboards and notice boards

The Magic filter is made for this: it removes the grey cast and glare and leaves the writing on clean white.

Documents you need to sign

Scan the document first, then add your signature with Sign PDF. That gives a much cleaner result than signing the paper and scanning it again.

What about the scanner built into my phone?

Both major phone platforms have a scanner somewhere. On Android, the Google Drive app has a scan button; on iPhone, the Notes and Files apps can scan documents. They are perfectly good, and if you already use them happily there is no reason to stop.

There are a few situations where a browser scanner makes more sense. You may not want the document stored in a cloud account, which is where the Drive scanner saves it by default. You may be on a work phone where you can’t install apps, or on a borrowed laptop with a webcam. Or you may want the same tool, with the same filters and size options, on every device. Whichever you use, the setup advice above applies equally.

Common mistakes

• Shooting on a white desk. The edges can’t be found, so you end up cropping by hand.
• Using Black & white on everything. It is great for text and terrible for a blue signature or a passport photo.
• Choosing Best quality for an upload form. The portal rejects it and you start again.
• Forgetting the order. Check the page thumbnails before you create the PDF; reordering afterwards takes longer.
• Cropping off the edges. Stamps, page numbers and reference codes often sit right at the margin.

Frequently asked questions