PDF & documents

How to Scan Documents With Your Phone and Get a Clean PDF

Capture, straighten, clean up and combine document photos into a professional multi-page PDF using nothing but a phone camera and a browser.

8 min read · Updated 2026-07-12

A phone camera at 12 megapixels resolves an A4 page at well over 300 DPI. It is, on paper, a better scanner than the flatbed most offices had a decade ago. The difference is that a flatbed controls lighting, flatness and geometry for you, and a phone does not. Get those three things right and you will produce documents indistinguishable from a real scan.

Capture: the part that determines everything

No amount of post-processing rescues a badly captured page. Spend the effort here.

Lighting

• Daylight, indirect. A table beside a window on an overcast day is close to ideal. Direct sunlight creates hard shadows and blown highlights.
• Flash off, always. On any glossy, laminated or plastic-covered document the flash produces a white hotspot exactly where you need to read.
• Light from the side, not behind you. If the light source is behind you, your head and phone cast a shadow across the page.
• Two sources beat one. A window plus a desk lamp on the opposite side flattens shadows nicely.

Geometry

• Phone parallel to the page. Tilting produces keystone distortion — the far edge is narrower than the near one — and text at the top of the page goes soft.
• Centre the page in the frame and fill it, leaving a small margin on all sides.
• All four corners visible. A clipped corner on a certificate is a rejection.
• Hold still. Brace your elbows on the table, or rest the phone on a stack of books. Motion blur is the difference between legible and not.

The page itself

• Flatten it. Fold creases cast shadow lines that look like marks on the document. Press the page under a heavy book for a few minutes first.
• Plain contrasting surface underneath. A dark table under a white page makes edge detection and cropping trivial.
• Remove plastic sleeves. They reflect and add glare. If a document must stay laminated, shoot at a slight angle to move the reflection off the text — then straighten in post.

Clean-up

Three operations, in this order.

1. Crop to the page edges with the Image Cropper. Everything outside the document is wasted file size and looks unprofessional.
2. Straighten. Even a two-degree rotation is visible and makes a document look sloppy. The cropper has rotation controls with undo.
3. Raise contrast. This is the step that turns "photo of a page" into "scan". In the Image Editor, increase brightness slightly and push contrast until the paper reads as white rather than grey and the text is solidly black.

That contrast step does more than cosmetics. A grey paper background is full of low-level noise that JPEG has to spend bytes encoding. Push it to clean white and the same document compresses to a fraction of the size while looking better.

Building the PDF

Most portals want a single PDF, not a folder of JPEGs. Use Image to PDF: add the images, arrange them in page order, and export. A few settings matter.

If pages end up in the wrong order, Organize PDF lets you rearrange them by dragging, and Rotate PDF fixes any page that came out sideways.

Getting under the size limit

A ten-page PDF built from full-resolution phone photos can easily exceed 40 MB against a 2 MB limit. Attack it in this order:

1. Resize the source images before building the PDF. 1600–2000 pixels on the long edge is ample for legible A4 text. This is by far the biggest saving and costs nothing you can see.
2. Compress the images to JPEG quality 80 before assembling.
3. Run the finished PDF through the PDF Compressor if it is still too large.
4. Split the document with Split PDF if the portal accepts multiple uploads and no single-file rule applies.

A note on text recognition

A scan produced this way is a picture of text, not text. You cannot search it, select it or copy from it. Making it searchable requires OCR (optical character recognition), which ConvertPro does not currently do.

For almost every upload scenario this does not matter — the officer reviewing your income certificate is reading it with their eyes. It matters if you are archiving documents you will later need to search, in which case a dedicated OCR tool is the right choice.

A repeatable checklist

• Flat page, plain dark surface, indirect daylight, flash off.
• Phone parallel and steady, page filling the frame, all corners in.
• Tap to focus on the text before shooting.
• Crop to the page, straighten, raise contrast until the paper is white.
• Resize the long edge to about 1800 pixels.
• Assemble into a PDF at A4 with a small margin, in the correct page order.
• Compress if needed, then open the result and read it end to end before submitting.

That last step catches more errors than everything else combined: a missing page, a page photographed twice, an upside-down back side, a thumb over a corner.

Frequently asked questions

Is a phone scan good enough for official submission?

Yes, provided it is sharp, straight, evenly lit, complete and legible. Portals and offices accept phone captures routinely. What gets rejected is a blurry, shadowed or partially cropped image — not the fact that a phone took it.

What resolution should I scan at?

For text documents, aim for roughly 200–300 DPI equivalent, which for A4 means about 1650–2500 pixels on the long edge. Beyond that you gain no legibility and pay for it in file size.

Should I scan in colour or black and white?

Colour, unless the portal specifies otherwise. Official documents often carry coloured stamps, seals and signatures whose colour is part of what verifies them. Converting to greyscale saves file size but can obscure a seal.

How do I combine front and back of a card into one PDF?

Photograph both sides, then add both images to Image to PDF in order — front first. You will get a two-page PDF. If the portal wants both sides on one page, place them as two images on a single page before exporting.

My PDF is 30 MB. What went wrong?

You built it from full-resolution photos. A 12-megapixel image is around 4 MB each, so eight pages is 32 MB before the PDF wrapper. Resize the images to about 1800 pixels on the long edge first — the PDF will typically land between 1 and 3 MB with no visible difference.

Are my documents uploaded when I use these tools?

No. Every step described here runs in your browser on your own device. The PDF is assembled locally and downloaded directly — nothing is transmitted to us or anyone else.