The Compare Files feature is available to Project Admins and users in a role with either download or manage access to both documents.

 

From the Documents tab:

 

1. Click on a file in your index to open it in the document viewer.
2. Click Compare and choose the file that you'd like to compare against the open document.
3. Click Compare to open both files in the viewer.
4. Click Start Comparison at the top.
   That button turns into a Show Comparison toggle that highlights all document differences.
   A Changes List appears on the right with Change sets. Each set has the number of characters that are different +/- for each pair of changes.
   
5. Click a Change set to highlight the differences in both documents.
   The document on the left is red and Old and the document on the right is green and New.