Paperbay guide
How to scan documents to PDF on your phone, free
Lay the page flat on a darker surface in even daylight, hold the phone straight above it, and let a scanner app find the edges, flatten the page and clean it up. Choose black and white for text, colour for anything with stamps, signatures or photos, and turn on searchable text so you can find the words later.
Set up the page
Most of a good scan happens before you press anything. A scanner app finds the page by the line where paper meets what is under it, and evens out the light afterwards, but it can't put back detail that was never in the picture.
- A darker surface. White paper on a wooden table, a dark worktop or a coloured folder gives a crisp edge. White on white (a page on a white desk) is the hardest case: put something darker underneath.
- Even light. Daylight from a window, or a ceiling light behind you, is best. Lean back so your head and the phone don't cast a shadow over the page.
- Flat paper. Unfold creases and hold curled corners down with something at the very edge, outside the page.
- Straight above. Hold the phone parallel to the page. A slight angle is fine (the page is flattened afterwards) but a steep one squashes the far end and loses sharpness there.
- Fill the frame. Get close enough that the page takes up most of the picture, with a little table showing on every side.
Scan it, step by step
This is how it works in Paperbay; other scanner apps follow much the same steps.
- Open the camera. Tap Scan. The first time, your browser asks to use the camera: the picture is only read on your device.
- Point at the page. A coloured outline snaps to the page's edges. With Auto on, hold still for about a second and the picture is taken for you; with Manual, tap the shutter.
- Turn the page and carry on. Each picture becomes a page straight away, so a ten-page letter is ten quick shots. Tap Save when you're done.
- Check the corners. If the outline missed (a hand on the page, a page on a white table), open the page, tap Corners and drag each one into place. A magnifier shows exactly where the corner sits.
- Pick a look. Colour, greyscale or black and white, with a strength slider. Turn left or right if a page is on its side.
- Save as PDF. Choose A4, US Letter or the scan's own shape, a file size, and searchable text, then share it, save it or send it to another app.
Already have photos of the pages? Choose them instead of the camera: the same edge finding and clean-up runs on each one.
Colour, greyscale or black and white?
Every look except Original first works out how the light falls across the page and divides it out, so a shadow or a yellow lamp doesn't leave the paper grey. Then:
| Look | Best for | File size |
|---|---|---|
| Black and white | Letters, forms, contracts, printed text, notes in dark pen | Smallest (pure black and white, packed tightly) |
| Greyscale | Pencil, faint print, pages with grey shading | Small |
| Colour | Anything with a coloured stamp, a signature in blue, highlighting, logos or photos | Larger |
| Original | When you want the photo exactly as taken, just flattened | Larger |
Black and white uses a local threshold: each part of the page is compared with its own surroundings, not with one setting for the whole page. That is why a shadow across half a letter doesn't turn that half black. Raise the strength for faint text; lower it if specks appear.
Paper size and file size
A4 (210 × 297 mm) is the standard almost everywhere; US Letter (8.5 × 11 inches) is used in the United States, Canada and a few other countries. Choose the one the person you're sending it to will print on. "Fit the scan" makes each PDF page the shape of the scan itself, which suits receipts, cards and tickets.
Rough sizes
A black-and-white page is often 50 to 150 KB. A colour page is a few hundred KB at the Standard size, less at Small. So a ten-page colour document is usually a few megabytes, comfortably under the 20 to 25 MB that many email services allow for attachments.
- Small is good for email and upload forms with a size limit.
- Standard keeps small print sharp and is right for most things.
- Best is for printing, and for pages with photos.
Searchable text
A scan is a picture of a page. Text recognition (OCR) reads the letters in it and places them, invisibly, over the picture in the PDF. The page looks exactly the same, but now you can search it, select a sentence and copy it, and so can screen readers.
In Paperbay the reading happens on your device, using the open-source Tesseract engine, in English, French, German, Spanish, Italian, Portuguese or Dutch. The reader (about 3 MB) and each language (under 3 MB) download once and then work offline. Your documents are searchable in the app too: type a word that was on the page and the scan comes up. Once the first page is read, a scan still called "Scan 12 Nov…" takes a name from its own words, such as "Invoice 1042, Harbour Joinery, 3 Nov 2026" (Undo puts the old name back, and a name you type is never changed).
Printed text in a clear typeface reads very well. Handwriting, tiny print, blur and decorative fonts read less well, so check names, numbers and amounts before relying on them.
ID cards, books and receipts
- An ID card or bank card. Scan the front, then the back, as two pages. In Share or save, turn on ID card: both sides on one page: both sides go on one sheet of A4 or Letter at a card's real size (85.6 × 54 mm), the way a photocopy would. Paperbay turns it on for you when the pages are card-shaped.
- An open book. Photograph both pages at once, then open the page and tap Split into two pages. It's split down the paper's true middle, worked out from the angle of the photo, so each page comes out straight.
- A receipt. Use colour and "Fit the scan", so a long receipt isn't shrunk onto a sheet of A4. To keep track of what you spent, send it to Receipts (below).
- Pages in the wrong scan. Open a scan's ⋯ menu and choose Add pages from another scan to join two into one, or open a page and choose Start a new scan from this page to split one into two.
Sign, lock or send it on
A scan is often the first step. In Paperbay, Send to another app hands it straight to another free Yuzool app on the same device, with nothing uploaded:
| To | Send | Open it in |
|---|---|---|
| Sign it or fill it in | The PDF | PDF Tools; the signed copy comes back to share or save |
| Put a password on it | The PDF | Lockbox |
| Black out an account number | A page | Redact |
| Keep track of what you spent | A page | Receipts |
| Listen to a letter | The text | Read Aloud |
| Add up a bill's lines | The table | Gridwork, when the words line up in rows and columns |
To merge the PDF with others, split it or make it smaller, save it and open it in PDF Tools.
Scanning private documents
Bank statements, medical letters and ID cards deserve care. Ask where the pictures go: many free scanner apps send your pages to a server to clean them up or read the text.
- Paperbay doesn't: the camera's pictures, the clean-up, the text reading and the PDF all stay on your device, and nothing is uploaded.
- Your scans are kept only in your browser's storage. Clearing the site's data deletes them, so save PDFs of the ones you need.
- To send something sensitive, black out what the other person doesn't need first with Redact, or lock the PDF with a password (Lockbox, or Paperbay Pro).
Common mistakes
- Your own shadow across the page. Move so the light is in front of you, or to the side.
- Shooting at an angle to avoid glare. A little is fine; a lot makes the far end soft. Move the page instead.
- Cutting off an edge. Leave some table showing all round, so the outline can find every corner.
- Black and white for a signed form. A blue signature becomes black and a red stamp may vanish. Use colour.
- Trusting the text blindly. A 1 and an l, or a 0 and an O, can swap. Check what matters.
Questions
Is a phone scan as good as a flatbed scanner?
For letters, forms, receipts and notes, yes, once the page is flattened and the light evened out. A flatbed still wins for photos you want to print large, glossy paper and bound books, because it lights the page perfectly evenly and touches it flat.
What does a searchable PDF mean?
The PDF carries the page's words as invisible text over the picture, so you can search, select and copy them in any PDF app. The page still looks exactly like the scan.
How big will the PDF be?
A black-and-white page is often 50 to 150 KB; a colour page a few hundred KB at a standard size. Ten pages in colour usually come to a few megabytes, well under the 20 to 25 MB many email services allow.
Is it safe to scan private documents in a browser app?
It depends on where the pictures go. Paperbay does everything on your device: the camera's pictures, the clean-up, the text reading and the PDF never leave it, and your scans are kept only in your browser's storage.
Can I put both sides of an ID card on one page?
Yes. Scan the front and the back as two pages, then turn on ID card in Share or save: both sides go on one sheet of A4 or Letter at a card's real size, 85.6 by 54 mm, like a photocopy.
Why does the text come out wrong sometimes?
Text reading guesses letters from the picture. Small print, handwriting, blur, a crease through a word or a fancy font all make it harder. Check names, numbers and amounts before you rely on them.