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wiera987 edited this page May 5, 2026 · 4 revisions

About PDFComp

Introduction

PDFComp extracts text from PDF files and compares them. The first thing to note is that it cannot compare images or the position/format of text. Even if the columns in a table are misaligned, it will not detect differences if the text is the same. A new experimental feature has also been added that allows you to compare text annotations such as font color, strikethrough, and underlining. Please keep these points in mind as you review the differences.

Operation

Auto operation

  • The Open button opens two PDF files. (Or drop the files into the window.)
  • Open the drop-down from the Compare Bookmark button and select a comparison mode.
  • The Jump to Prev/Next buttons (<- and ->) move to the next difference marker.
    • Pages that have not been compared yet are compared automatically before moving to the next difference marker.
    • The pen button (Jump to Diffs) switches jumping to the next difference marker, and the page button (Jump to Pages) switches jumping one page at a time.
    • The Static button makes markers static, and the Blinking button switches markers to blinking.

Manual Operation

  • Each Compare button highlights differences in the comparison range. (Space key)
    • If there are already difference markers in the comparison range, they are cleared and the range is compared again.
    • Page-pair information can be cleared from the Clear All Markers menu.
  • The << and >> buttons move the pages of both PDF files at the same time. (Left arrow and Right arrow keys)
  • The < and > buttons move the pages of each PDF file independently. (Ctrl+arrow keys, Alt+arrow keys)
  • The Clear Markers context menu clears highlighted difference markers.
  • The Copy Text context menu copies text.
  • The Copy Image and Copy Bookmarks menus copy PDF images and bookmark text.
  • The Find... menu opens the text search window. You can search each PDF separately.

Use Compare Page when you want to compare one page at a time in manual operation.
Use Compare Bookmark or Compare Document when you want to compare across multiple pages.
Compare Bookmark compares pages by the range of the selected bookmark. Pages without bookmarks are compared together as one grouped range.
Compare Document compares the entire document at once without considering bookmarks.

Pan mode lets you drag the PDF to scroll.
Text mode lets you select and copy text.
Bounds mode lets you specify the comparison range for each PDF. Results outside the selected range remain as they are, and the specified range is compared again.

[!] The comparison range specified with Bounds mode applies to all pages included in the selected comparison mode. To compare only the currently visible page, use Compare Page.

Fit One Page changes the PDF display to fit the window size.
Fit Width changes the PDF display to fit the width of the window.

Usage tips

  1. How to use the comparison modes
  • If you want to compare one page at a time manually, use 'Compare Page' as before.
  • If bookmarks are included, 'Compare Bookmark' is recommended. Since the text is compared while referring to the chapter structure of the currently selected bookmark item, it will be compared on a chapter-by-chapter basis even if the number of pages per chapter differs. In addition to comparing the chapter of the current page, you can also select an item from the bookmark pane and compare a specified chapter.
  • Use 'Compare Document' when bookmarks are not included. It compares the entire file at once according to the text sentences without considering the chapter structure.
  1. In Bounds mode, you can select one part of a page to compare. Examples of applications include:
  • Comparing only the main text while ignoring headers and footers.
  • Select specific parts of long paragraphs or tables to compare them more closely.
  • When you want to carefully re-compare parts that you couldn't compare properly before.
  1. About 'Next different page' and 'Previous different page' These functions are useful when first checking the differences between PDF files, as they move to pages that contain differences while comparing the documents. The behavior when moving between pages differs slightly between Page Comparison and Bookmark/Document Comparison.

  • Compare Page
    Since this mode compares one page at a time, both PDFs advance by one page and are compared. If no differences are found, it continues to the next page.

  • Compare Bookmark / Compare Book
    These modes first compare the target range at once, then jump to pages that contain differences. One page in the left PDF does not always correspond to one page in the right PDF. For example, if the right PDF contains more text for the same section, it may span multiple pages. In such cases, only the right-side pages advance.

[!] When you specify an area in Bounds mode, the difference within that area is judged, and differences outside the area are not considered differences.

  1. If you are having trouble with the display scaling when you adjust the window size to change the copy size, you can set Fit Width to adjust the display range in the height direction as long as the width is kept constant.

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