Compare PDF 

Compare PDF can compare both - related and non-related Adobe Acrobat files. "By keywords" comparison feature highlights common and unique keywords, allowing to compare non-related files. Word-by-word comparison compares files with a common ancestor
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PDF Studio 

PDF Studio is a standalone application to add text and images, and to split or merge PDF documents. Common actions can be saved as stamps to be reused with a single click. PDF Studio works on Windows, Mac and Linux and does not require Adobe Acrobat.
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Compare Suite 

Compare Suite can compare both - related and non-related files. "By keywords" comparison feature highlights common and unique keywords, allowing to compare non-related files. Word-by-word comparison compares files with a common ancestor.
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WinMerge 

WinMerge is a tool for visual difference display and merging, for both files and directories. Unicode support. Flexible syntax coloring editor. Windows Shell integration. Regexp filtering. Side-by-side line diff. Highlights differences inside lines.
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