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Compare PDF

Compare PDF shows what changed between two versions of a document. Add the original and the revised file, and the tool lines up their text word by word. Removed words are struck through in red, added words are underlined in green, and a change list lets you jump from one edit to the next. Switch to the visual view to catch changes that text can't show, such as a moved logo, a new signature or a swapped image, with overlay, side-by-side and slider modes. You can ignore case or punctuation, and export an HTML report, a CSV change list or an overlay PDF. Both files stay on your device, which suits contracts and tenders.

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Original (A)

Changed (B)

No files handy? .

How to use

01

Add both versions

Drop the older file in Original (A) and the newer one in Changed (B). Use the swap button if you put them the wrong way round, or try the two sample agreements first.

02

Review the text changes

Read the side-by-side view or switch to Redline. Click an item in the change list, or use the up and down arrows, to jump between edits. Tick Ignore case or Ignore punctuation to hide small edits.

03

Check visuals and export

Open Visual changes to see the pages in overlay, side-by-side or slider view, and click Find pages with changes to scan the whole file. Download an HTML report, a CSV change list or an overlay PDF.

Why Compare PDF

How the text comparison works

Both files are read line by line and the lines are matched in order. In long documents, lines that appear only once in each file act as anchors, and the lines between anchors are matched as closely as possible. Where lines differ, the words inside them are compared again. That second pass is why a single changed word in a reflowed paragraph shows up as one word, not as a rewritten paragraph.

Unchanged text is folded away so the changes stand out. Tick Show unchanged text to read the whole document with the edits marked in place.

Reading the three visual views

Each view answers a slightly different question about the same pair of pages.

  • Overlay fades the page to grey and colours only the differences: red for ink that was removed, green for ink that was added, orange for a colour change.
  • Side by side shows both pages with boxes around each changed area.
  • Slider stacks the new page on the old one. Drag the handle to wipe between them and spot shifted lines.
  • Find pages with changes scans every page pair at low resolution and lists the ones that differ.

Common questions

How do I compare two PDF files for differences?
Add the older version as Original (A) and the newer one as Changed (B). The text of both is read and compared straight away. Removed words show in red, added words in green, and the counts at the top tell you how many changes there are. Open Visual changes to compare the pages as images.
What is the difference between text and visual PDF comparison?
Text comparison looks at the words and ignores layout, so it finds edits even when a paragraph moves to another page. Visual comparison draws both pages and compares the pixels, so it finds changed images, logos, signatures, colours and spacing, but it can't tell you which word changed. Use both for anything important.
Can I compare a scanned PDF with a digital one?
Visually, yes. The Visual changes tab works on any pages, scanned or not. Text comparison needs real text, so a scan shows a message instead. Run the scan through OCR PDF first, then compare the OCR'd copy, keeping in mind that OCR mistakes will show up as changes.
Why does a PDF comparison flag changes I can't see?
Two files can look alike but store text differently. A hyphen may become a dash, quotes may change from straight to curly, or a word may be split across two runs. Ticking Ignore punctuation hides most of these. Visual comparison can also flag tiny shifts in position, and the Sensitivity slider hides those.
Can I compare PDFs that have different page counts?
Yes. Text comparison reads each file as one continuous document, so added or removed pages simply show up as added or removed text. In the visual view, untick Move both together, pick the matching pages on each side, then tick it again to keep that offset as you page through.
How do I save or share the results of a PDF comparison?
Use Download report for a single HTML file with every change marked, which opens in any browser and can be emailed. Download change list gives a CSV with one row per change and its page numbers. Download overlay PDF saves the visual comparison of every page pair.
Are my documents uploaded when I compare them?
No. Both PDFs are opened and compared by code running in your browser tab, and nothing is sent to a server. You can close the tab when you are done and no copy is left anywhere.
Does Compare PDF detect changes in fonts, tables or images?
The text view compares words, so a change of font, size or bold is not listed there. Changes inside tables are listed when the words or numbers change. The visual view catches font, image, table border and layout changes, because it compares how the pages actually look.
Is there a size or page limit when comparing PDFs?
Each file can be up to 150 MB. There is no page limit, but everything runs on your device, so very long documents take longer to read and the visual scan of every page takes the longest. A laptop handles large files better than an older phone.

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