At times you will need to read two PDF documents side by side to compare contents, make changes, and even copy content from one to the other. Whatever the issue is, with Foxit Reader, you’ve got three easy ways to do it. You can allow multiple instances of Reader to be open at the same time,tear a tab out to become a new window or use the Split View feature.
Allow multiple instances
To bring up an additional Foxit Reader window, just enable the “allow multiple instances” feature. Just go to File -> Preferences -> Documents -> and check “Allow multiple instances”.Now whenever you double-click a new PDF file, Foxit Reader will open in a separate window.
Tear a tab out
When you open some PDF files in multiple tabs in a single Foxit Reader window, please drag and drop a file tab outside of the existing window to create a new instance and view the PDF file in that individual window.
Note: This method is available in Foxit Reader 9.4 and higher versions.
If you want a side by side—or top and bottom—comparison of different pages within the same document, you can use Foxit Reader’s split view feature to view different instances of a document within the same tab. To do this, simply click View > Split, then choose whether you want to split your view vertically or horizontally.
With this feature, you can scroll, zoom, or turn to other pages in one pane without having it affecting the other.
With Foxit Reader, all it takes is a few clicks to view two or more files at once without having to switch back-and-forth between tabs.
In addition,if you want to use Foxit application to compare a revised PDF to an earlier version and highlight the differences between two PDF files automatically for you.
Foxit Reader doesn't have such feature,you have to use the "Compare" feature under the "View"tab in Foxit PhantomPDF to do that.