How to Scan Documents to PDF With Your Phone
Short answer
Do not photograph documents with the camera app. On iPhone, open Notes → camera icon → Scan Documents, or Files → ⋯ → Scan Documents. On Android, use Google Drive → + → Scan or your phone's built-in scanner. These detect the page edges, correct the perspective and produce roughly 200KB per page instead of 4MB.
On this page
Someone asks you to send a signed form. You photograph it on the kitchen table, attach it, and send a 4.8MB image of a sheet of paper at an angle, half in shadow, with a mug visible in the corner.
Your phone has had a proper document scanner built in for years, and it is sitting two taps away. It finds the page edges, corrects the perspective so the page is rectangular, flattens the lighting, and saves a multi-page PDF at roughly a twentieth the size.
Why scanner mode beats the camera
| Camera photo | Scanner mode | |
|---|---|---|
| Size per page | 3–5MB | 150–300KB |
| Page edges | Whatever was in frame | Cropped to the document |
| Perspective | Keystoned if angled | Corrected to rectangular |
| Lighting | Shadows and glare preserved | Flattened and contrast-boosted |
| Multiple pages | Separate image files | One PDF |
| Output | JPEG |
The size difference alone settles it for anything going into an upload form with a limit. But the perspective correction is what makes the result look like a document rather than a snapshot — scanner modes detect the four corners of the page and warp them back to a rectangle, which no amount of cropping afterwards achieves.
On iPhone
Two routes, both built in. Neither needs an app installed.
The Notes app
The quickest, and the one that lets you add pages later.
- Open Notes and start a new note.
- Tap the camera icon above the keyboard.
- Choose Scan Documents.
- Hold the phone over the page. A yellow overlay appears when it finds the edges, and it captures automatically — or tap the shutter to capture manually.
- Scan each page in turn. The counter at the bottom right shows how many you have.
- Tap Save.
- To get a PDF out, tap the scan in the note, then the share icon, then Save to Files — or share it directly to Mail or WhatsApp.
The advantage of Notes is that the scan stays editable. Reopen it, tap the camera icon again, and you can add pages, re-crop existing ones or delete a bad shot.
The Files app
Better when you want the PDF saved to a specific folder straight away.
- Open Files and navigate to where the PDF should live.
- Tap the ⋯ button (top right).
- Choose Scan Documents.
- Scan the pages the same way.
- Tap Save — the PDF is written to the current folder.
Adjusting an iPhone scan
After capturing, before saving, you get four controls at the bottom of the screen:
- Crop handles — drag the corners if the automatic detection missed.
- Filter icon — switch between Colour, Greyscale, Black & White and Photo. Greyscale or Black & White on a text document cuts the file size substantially.
- Rotate.
- Bin — discard the page and retake it.
The filter is the setting most people never touch and the one with the biggest effect on file size. For typed text on white paper, Black & White produces the smallest and often the sharpest result. For anything with a photo, a stamp or shading, stay on Greyscale or Colour.
On Android
Android has more routes than iPhone and they vary by manufacturer, so check two or three.
Google Drive
The long-standing option, available on essentially every Android phone.
- Open Google Drive.
- Tap the + button (bottom right).
- Tap Scan.
- Point at the page and capture.
- Crop with the handles, apply a filter, then tap the + to add further pages.
- Tap Save, name the file and choose a Drive folder.
One thing to be aware of: Google has been moving scanning toward a more prominent, dedicated experience rather than leaving it buried under Drive’s + menu. On newer devices and newer app versions you may find the scanner as its own tile in Drive, surfaced in the Files app, or as a separate shortcut on the home screen. The capture flow is the same wherever it lives — if + → Scan is not where you expect, look for a Scan tile or search your app drawer for “scan”.
Your phone’s own scanner
Many manufacturers include one, and it is often better integrated than Drive’s:
- Samsung — the camera app detects documents automatically and offers a Scan prompt; Samsung Notes also has a scanner.
- Pixel — scanning appears in the Files app and in Drive.
- Xiaomi, OPPO, Vivo — usually a Document mode in the camera app.
Microsoft Lens
Worth installing if you scan regularly and want control. It offers explicit Document, Whiteboard and Business Card modes, produces reliably clean output, and exports to PDF, Word or OneNote. It is free and available on both platforms.
Getting a good scan
The scanner fixes geometry. It cannot fix light.
Lighting. Even, indirect light is everything. Stand so your own shadow does not fall across the page, and avoid direct overhead spotlights, which produce a bright hotspot in the middle and dark corners. Daylight near a window, with the page not in direct sun, is ideal. Avoid using the flash — it creates a glare circle on glossy paper.
Background. Put the page on a surface that contrasts with it. White paper on a white table defeats the edge detection; white paper on a dark wooden table is detected instantly.
Hold it flat. Fold creases and curl cause the text to bend. Press the page flat, or weight the corners. A page from a bound book will never flatten completely — scan each side separately and accept the curve near the spine.
Hold the phone parallel. Perspective correction works, but it works by stretching pixels, and extreme angles leave one side of the page blurrier than the other. Directly overhead gives the cleanest result.
Check before you leave. Look at each captured page before tapping Save, particularly any page with small print or a signature. Retaking a page takes ten seconds; re-scanning the whole document from scratch later takes much longer.
Multi-page documents
Scan everything in one session. Both iPhone and Android scanners keep adding pages to the same document until you save, and once a PDF is written you cannot append to it without a separate merge step.
Keep the pages in order as you go — reordering after the fact is fiddly on a phone. If you capture a page out of sequence, delete it and retake rather than trying to shuffle later.
For a long document, check the running file size occasionally. Twenty colour pages at default settings can reach 15MB, which will fail plenty of upload forms. Switching to greyscale before you start avoids having to compress afterwards.
If the file is still too big
A phone scan at default settings is usually fine, but colour mode on a long document can push past an upload limit.
In order of what to try:
- Re-scan in greyscale or black-and-white. The cleanest fix, since you avoid creating the data rather than discarding it.
- Compress the PDF. Our PDF compressor runs in your browser, including on a phone, so the document never leaves your device — which matters, because phone scans are overwhelmingly personal paperwork.
- Split it, if the form accepts multiple files.
The threshold for readability and how to check it is covered in compress a scanned PDF without making it unreadable.
What not to do
- Do not use the camera app and then convert the photos to PDF. You get distortion, shadows and a file twenty times larger than it needs to be.
- Do not install a free “PDF scanner” from the app store when your phone has one built in. Most are wrappers around the same OS scanning API, loaded with adverts, and many upload your documents to their own servers.
- Do not scan in colour by default. It is the single biggest unnecessary contributor to phone scan file size on text documents.
- Do not scan through a plastic wallet or laminate. The glare is worse than any filter can fix. Take the document out.
- Do not assume the scan is searchable. A scan is an image. If you need to search or copy the text, you need OCR — see make a scanned PDF searchable.