How to Scan Documents With Your Phone Into a Clean PDF

Scanning on an iPhone

Apple's support page describes two built-in scanners. Notes keeps the scan inside a note; Files saves it as a document in a location you choose.

In Notes:

Open Notes and select a note or create a new one.
Tap the Attachment button, then tap Scan Documents.
Point the camera at the document. In iOS 26 you can also choose flash or an image filter.
In Auto mode the page is captured on its own. Otherwise tap the Shutter button or press a Volume button. Drag the corners to fit the page, then tap Keep Scan.
Scan the next page, or tap Done.

In Files: tap the More button, then Scan Documents. Capture and adjust the pages the same way, tap Keep Scan and Done, choose a location and tap Save.

Scanning on Android with Google Drive

Google's help page for Android uses the Google Drive app:

Open the Google Drive app and tap Camera at the bottom right.
Point the camera at the document and take the photo. You can switch between Manual and Auto capture.
Adjust the scan: Crop & Rotate to change the area, Filter for color or grayscale, Clean to erase stains and fingers, Add to scan another page, Retake or Delete for a bad page.
Tap Done, then enter a file name or pick a suggested title.
Choose .pdf or .jpg, optionally tap Location to pick a folder, and tap Save.

Google says these scans are saved as searchable PDFs on your Google Drive. That means the pages are stored in your Drive account, not only on the phone.

Light, angle and background

Both scanners find the page edges for you (Google shows them as a blue outline), but they can only work with what the camera sees. These habits make the biggest difference:

Even light from the side or above, such as daylight from a window. A ceiling lamp straight above casts the shadow of your phone onto the page.
No glare. On glossy paper the flash leaves a white spot where text disappears. Turn the flash off and add room light instead.
A dark, plain background. White paper on a dark table gives clean edges for the automatic corner detection.
Hold the phone parallel to the page, centered, close enough that the page fills most of the frame.
Flatten the page. Folds and curled corners bend the lines of text. A book spine is the hardest case; press the page flat with a hand outside the frame.

Straight lines matter for more than looks. The Tesseract OCR documentation says the quality of its line detection drops significantly when a page is too skewed, and that an uneven background darkness hurts the step that separates text from paper.

Resolution and file size

Resolution in a scan is pixels per inch of paper, usually called dpi. The page size times the dpi gives the pixels you need. The table shows Letter and A4 at the three common settings, with the size of the raw image in memory before compression: three bytes per pixel in color, one in grayscale.

Paper	DPI	Pixels	MP	Raw color	Raw gray
Letter	150	1,275 × 1,650	2.1	6.3 MB	2.1 MB
Letter	200	1,700 × 2,200	3.7	11.2 MB	3.7 MB
Letter	300	2,550 × 3,300	8.4	25.2 MB	8.4 MB
A4	150	1,240 × 1,754	2.2	6.5 MB	2.2 MB
A4	200	1,654 × 2,339	3.9	11.6 MB	3.9 MB
A4	300	2,480 × 3,508	8.7	26.1 MB	8.7 MB

Two things follow. First, the pixels have to cover the page, not the whole photo: for 300 dpi on Letter, the page itself must span 2,550 pixels across in the picture. Fill the frame and the phone has a better chance of reaching it. Second, doubling the dpi quadruples the pixels: a Letter page at 300 dpi has 4 times the pixels of the same page at 150 dpi. JPG compression inside the PDF makes the file much smaller than the raw size, but the starting point is four times as large.

A practical split: 150 to 200 dpi for documents you send or read on screen, 300 dpi when the text should be recognized or the page might be printed. Grayscale is enough for plain text and cuts the raw data to a third. For pixels per inch in photo prints, see the photo print sizes guide.

From photos to one clean PDF

Sometimes the pages are ordinary photos: taken with the camera app, sent by someone else, or scanned as .jpg. Turn them into one PDF in this order:

Convert HEIC. iPhone photos are often saved as HEIC, a format not every app opens; HEIC photos explained says why. The HEIC to JPG converter turns them into JPG in your browser.
Make the PDF. Put the images in order in JPG to PDF, rotate any sideways page, and choose Letter or A4 so every page has the same size.
Combine files. If some pages are already PDFs, merge PDF puts them into one file and can add JPG or PNG images as pages.
Shrink it last. Compress PDF recompresses the page images, with a grayscale option and a target size for upload limits.

For sideways pages, the wrong page order or blank backs in a file you already have, how to fix a scanned PDF goes through the repairs in the right order.

Making the text searchable

A scan is a picture of text. Until optical character recognition reads it, you cannot search it, select a sentence or copy a number. OCR PDF adds an invisible text layer to a scanned PDF, so the pages look the same but Ctrl + F works. It draws each page at 200 or 300 dpi before reading; the Tesseract documentation says the engine works best at 300 dpi or more, so a 300 dpi scan gives it the most to work with. For a single photo of a receipt or a page, image to text gives you the text to copy without making a PDF.

Privacy: cloud scanning vs on-device

Scans are often the most sensitive files on a phone: IDs, bank letters, tax forms, medical bills. Where they are processed and stored matters.

Cloud scanning: the Google Drive scanner saves to your Drive account. That is convenient for access from a computer, and it also means the file sits with the provider under your account's security. A strong password and two-step sign-in matter more than usual.
Built-in phone scanners: in Files you choose the location yourself. A folder on the phone keeps the scan local; a cloud folder syncs it.
Third-party scanner apps: check whether the app processes pages on the phone or uploads them, and what its privacy policy says about keeping them.
Browser tools: every tool linked on this page runs in your browser. The images and PDFs are processed on your device and are not uploaded.

If a service that holds your scans reports a breach, what to do after a data breach lists the steps to take.

Frequently asked questions

What resolution should a scanned document be?

For reading on screen and sending by email, 150 to 200 dpi is usually enough. For text recognition, aim for 300 dpi: the Tesseract OCR documentation says it works best on images of at least 300 dpi. A Letter page at 300 dpi is 2,550 by 3,300 pixels.

How do I scan a document on an iPhone?

Apple describes two ways. In Notes, open a note, tap the Attachment button and choose Scan Documents. In Files, tap the More button and choose Scan Documents, then pick a location and tap Save. In both, you adjust the corners, tap Keep Scan, and tap Done when all pages are in.

How do I scan a document on Android?

Google describes scanning with the Google Drive app: tap Camera at the bottom right, take the photo, then use Crop & Rotate, Filter, Clean or Add for more pages. Tap Done, enter a file name, choose .pdf or .jpg, and tap Save. The file is stored in your Google Drive.

How do I turn several phone photos into one PDF?

Convert any HEIC photos to JPG, then put the images in order in a JPG to PDF tool and choose A4 or Letter pages. If you already have separate PDFs, merge them into one file. Compress the result last, after all pages are in.

Is it safe to scan documents with a free scanner app?

It depends on where the app processes and stores the pages. Before you scan an ID or a tax form, check whether the app works on the phone or uploads to a server, and where the files end up. Tools that run in the browser and do not upload, such as the ones linked here, keep the pages on your device.

Sources

Written by Tobias. Updated October 26, 2026.