Processing large documents can require several minutes.
Both documents should be different revisions of the same document, representing older and newer versions.
Ensure both documents are exported as PDFs using identical export settings and that they are similar in file size (KB or MB).
If one document is significantly larger than the other, Delta Docs will still attempt the comparison, but it may generate false positives since it identifies differences between the two.
If one document contains more pages than the other, Delta Docs will match pages to their most likely corresponding earlier version.
If a page has no similarity to any page in the other document, Delta Docs will insert a blank page into the corresponding column to maintain alignment.