Compare PDF Documents with ComPDFKit

By ComPDFKit | 2022 Oct 14

This article talks about comparing two PDF files. You will see what it is, where to use it, and the types of PDF comparing. You are welcome to ask, inquire, or discuss any PDF features with the ComPDFKit team. 



What Are PDF Comparing?


Let’s get to know PDF Comparing. Comparing two PDF documents is to see the differences between these two documents. Of course, there are some ways to mark the different places, such as inserting, missing, and editing words. Then, you could check the differences and maybe make some changes. After comparing the PDFs, a new file with the marked changes will be generated.


Generally, there are some occasions for us to compare files:


         - Different versions of files: Assume that you have two PDF files that are about your two products. There are just some words that need to be adapted. And now, you can compare these files to see whether all the related words are changed.

         - Some similar files: In this situation, maybe your customers find some illegal copies and need to find all the differences. Then the file with the consequences needs to be saved.

          - Check what you did in your files: When you accidentally update some contents in an old document and convert it to a PDF file, you need to see the differences between the old and new versions of the PDFs. So that you could avoid doing all the work you did before.



PDF Content Comparing


ComPDFKit supports comparing the contents of two PDFs. The content comparison needs to compare each character. For easy reviewing, the differences between these compared PDFs need to be marked with colors. And there will also be a document to display the differences.


Settings of Comparison:

Let’s think about how many kinds of differences would be between two similar PDF documents. Yes, all the situation would be if some words are deleted, added, or replaced. So, you need three colors to mark the differences. And you could set the color according to their personal preference with the technologies of ComPDFKit PDF SDK. 


Except for the kinds of changes, you could choose the ranges of each PDF file to compare.


Results of Comparison:

The resulting document combined with the two compared PDFs. We could see the marked places in different colors. There is a review workflow for you to track each change. You could also skip to the next or last changes in this result document.



At last, you could save the following documents:

         - The original document and with marked annotations.

         - The second version of the PDF with marked colors annotations.

         - The resulting document combined with two PDF versions. 



Compare PDFs: Overlay


The overlay method of comparing PDFs is similar to the content comparison. We will just focus on the special part. The results comparison document merged the two compared PDFs. We could see all the changes in the result documents.


So, we need to think about how to mark the changes between the two versions of PDFs. We could mark these two PDF versions with two different colors. Then, align these documents. The blend color would appear if there are strokes in two PDF versions at the same place. You could choose the blending modes like normal, darken, lighten, etc.


You could also set the opacity of the strokes in these two PDFs. With the different colors in the result document of comparison, you could see where the strokes are deleted or added. 



Final Words!


A lot of PDF features could be used after comparing two PDFs such as editing the PDFs. If you have some questions about ComPDFKit, please contact us.