When a Document Appears Twice

When using a document twice or more in a merge (for instance, merging A.pdf pages 1-3 followed by B.pdf followed by A.pdf pages 4-6) cpdflib needs to know that both instances of A.pdf refer to the same file, so it can share common objects in the output, avoiding content shared between pages (e.g fonts) being included twice.

The function MergeSame is equivalent to Merge, but an array of strings is also passed: these would typically be the filenames of the documents - but can be any strings which allow cpdflib to distinguish multiple instances of the same file.