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CornerTools

Compare PDF

Find every difference between two PDFs — changed text side by side and visual changes highlighted — without uploading them.

Original PDF

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Changed PDF

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Shows what changed between two versions of a PDF, such as a contract, a notice or a form, so you do not have to read both line by line. The text view lines up the two documents paragraph by paragraph and marks the words that were added, removed or changed; the visual view lays the pages over each other and boxes whatever looks different, pictures and layout included. Both PDFs stay on your device.

How to use it

Add the original PDF and the changed one; a PDF with a password asks for it. Their text is read as they open, and the comparison appears below.

  • Text: the paragraphs side by side, or Unified with each change's old text above its new, each labelled with its page. The arrows step through the changes; Hide unchanged folds the paragraphs between them. Download changes saves the list as a text file.
  • Visual: one page at a time, the original on the left of the split and the changed PDF on the right. Drag across the page, or use the slider, to move the split; the changed areas are boxed. The page list says which pages differ, and which were added or removed.

In the text view's options, Ignore headers, footers and page numbers (on) leaves out lines that repeat at the top or bottom of pages, and page numbers, which otherwise change on every page after an inserted one. Ignore whitespace (all) and Ignore case (off) set what counts as a change.

How it works

Each PDF's text is taken in reading order, as PDF to Text takes it, and each paragraph's lines are joined into one. The two lists of paragraphs are then compared as a text diff compares lines, and a reworded paragraph is compared word by word. Because whole paragraphs are compared, text that an edit only re-wrapped onto different lines is not a change. Scanned pages have no text to compare until they are read with OCR, which the tool offers when it finds them.

For the visual view, pages are paired by their text, so a page inserted in the changed PDF shows as added rather than making every later page differ. Each pair is drawn at 100 DPI and compared pixel by pixel; a pixel counts as changed only when nothing near it in the other drawing matches it, so the soft edges of letters, which shift by a pixel between two drawings of the same text, do not.

Examples

A changed word in a re-wrapped paragraph

Original
The tenant shall pay the rent on the first
day of each month, by bank transfer.
Changed
The tenant shall pay the rent on the fifth day
of each month, by bank transfer.

With the default options: “1 paragraph changed in 1 place”, with only “fifth” marked in the changed PDF. The words “day” and “of” moved to other lines, but within the paragraph they are where they were.

Frequently asked questions

The text view compares the text on the pages, filled-in form fields included. Comments and other annotations, bookmarks, and the PDF's properties (title, author) are not compared. A change in font, colour or position with the same words shows only in the visual view.
Save the Word file as a PDF first (File, Save As, PDF in Word), then compare the two PDFs. To compare plain text, use Text Compare.
No. Your browser reads, compares and saves the files on your device; they are not sent to CornerTools or anyone else, and neither is a password you type. To check, open the browser's developer tools at the Network tab and add a PDF: no request carries it. The PDF engine downloads from this site the first time you use it: a download to your browser, not an upload of your file.

See also