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AECbytes Tips and Tricks Issue #13 (December 28, 2006)

Automatic Comparison of Two PDFs

John TeSelle
Founder, LineType Software, Inc.

A powerful feature of Adobe Acrobat (version 5.0 or version 6.0 and 7.0 Professional) is the ability to compare two versions of a PDF document and create a third document with the differences highlighted. Although this feature is probably not needed by most people on a day-to-day basis, when it is needed, it is great to have.

Consider a situation in which two different sets of construction documents have been created at different times (such as an early-release set and a final set) and it is necessary to determine what has changed between the two. Doing this the old fashioned way is one of the most boring tasks imaginable, and you can never really be sure that you have checked everything. It can easily be automated using Acrobat.

As an example, two versions of a detail sheet are shown here:

Version 1. (Click here to see the actual PDF).

Version 2. (Click here to see the actual PDF).

Can you spot the four differences in these two files? Here's how to automate this process with Acrobat.

The menu location of the Compare function varies in different versions of Acrobat, but in Acrobat 7.0 Professional it is found under Document > Compare Documents…

The dialog box has several settings. The ones shown below are recommended for comparing drawings.

  • Select the two documents in the dialog box windows as shown (Version1.pdf and Version2.pdf are shown here).
  • Choose Page by page visual differences and Normal analysis as the comparison options. You can experiment with the other comparison options, but these seem to provide good results at a reasonable speed.
  • Choose Side by Side Report—the consolidated option does not seem to work well for drawings.
  • Click OK.

Acrobat will then create a new PDF file containing two header pages that summarize the comparison, and duplicates of the compared pages with the differences highlighted inside magenta hexagons. The comparison report generated from the examples above is shown below.

Comparison Report . (Click here to see the actual PDF).

It may be necessary to zoom in on the duplicate pages to see the highlighted areas.

Note that the comparison feature is not included in version 6.0 and 7.0 of Adobe Acrobat Standard. It is included in version 5.0 of Acrobat, and in version 6.0 and 7.0 Professional.

About the Author

John TeSelle is a practicing architect in Nashville, Tennessee. He is the founder of LineType Software, Inc., which develops plug-ins for Adobe Acrobat and Reader for the AEC industry. He is an authority on the use of PDF and PDF-based digital signatures for architects and engineers, and has shared this expertise with professionals across the country in seminars and webcasts sponsored by Adobe Systems, Inc. He can be reached at info@linetype.com.

 

 

 

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