How to edit a scanned PDF on a Mac

With PDF Unlimited (free)

1. Open the scan

   Open the scanned PDF in PDF Unlimited. If pages are sideways, rotate them first with ⌘L or ⌘R.

2. Make it searchable

   Choose Tools > Make Searchable (OCR). Now you can search, select and copy the text, and it is ready for the steps below.

3. Add or correct text

   Switch to Annotate mode and use the text box tool to type anywhere. To replace a word, draw a rectangle with a white fill over it, then put a text box on top.

4. Mark it up and sign

   Highlight, underline or add notes in Annotate mode. Switch to Sign mode to place a drawn or typed signature.

5. Remove sensitive details

   For account numbers or names that must truly go, use Redact mode and then Tools > Apply Redactions…. A white box only hides; redaction removes.

6. Fix the pages and save

   In Pages mode, reorder, delete or insert pages, and use the Crop tool to trim scanner borders. Save, and use File > Export Compressed… if the scan is heavy.

With Preview, built into macOS

1. Embed text

   Open the scan in Preview, choose File > Export and select Embed Text if it appears, then save.

2. Show the Markup toolbar

   Click the Show Markup Toolbar button. Use the Text tool to add words and Shapes to draw a rectangle.

3. White out a word

   Select the rectangle, set its Fill Color to white and its border to none, drag it over the word, then add a text box on top.

Why scans are hard to edit

When you scan a page, the scanner takes a photo. The PDF it produces holds that photo and nothing else. There are no letters in it, only pixels arranged to look like letters. That is why you cannot click into a sentence and fix a typo the way you can in a digital PDF with Edit mode.

OCR (optical character recognition) reads the photo and adds real, invisible text underneath. That makes the scan searchable and copyable. It does not turn the page into a word processor document; the photo is still what you see. More on that in how to make a PDF searchable.

What you can edit on a scan

Quite a lot, as long as you work on top of the page rather than inside it:

• Add new text anywhere: dates, names, corrections. See add text to a PDF.
• Fill in a scanned form with text boxes. See fill out a PDF form.
• Highlight, underline, draw arrows and leave notes. See annotate a PDF.
• Sign it. See sign a PDF on Mac.
• Remove sensitive details for real. See redact a PDF.
• Rotate, crop, reorder, delete and add pages. See add pages to a PDF.

The white-out trick, and its limit

Covering a word with a white rectangle and typing over it is the classic fix, and on a clean white scan it is hard to spot. On grey or textured paper the patch shows, so match the fill color to the page if you can.

Remember that a white box only hides the word visually. The original is still underneath, and after OCR it is still in the text layer. If the goal is privacy rather than tidiness, use true redaction instead.

When you need to rewrite the whole thing

If the document needs real rewriting, not a few corrections, rebuild it. Run OCR, choose File > Export > As Text… in PDF Unlimited, and paste the text into Pages or Word. Fix the wording there, then export a fresh PDF. Check the recognized text against the scan, especially numbers. Our PDF to text guide covers this in more detail.

PDF Unlimited's Edit mode retypes real text in digital PDFs, but not on a scan. The OCR layer is invisible text behind a photo, so there is nothing visible to rewrite; if you click it in Edit mode, the app says so and points you to a text box. Apps that claim to edit scanned words still rely on OCR guesses, so proofread whatever they produce.

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