Opening earlier versions saved inside a PDF

Inside many PDFs sits more than one document. When a file is saved incrementally, the changes are added to the end and the earlier state stays inside the file. Over time a single PDF can hold a whole history of itself. PDF by Zaweba lets you look at that history directly: File, then Earlier versions opens each incremental save of a document in a tab of its own.

Why PDFs keep their history

Incremental saving is a sensible design. Rather than rewriting a whole file to change one word, a program can add only what changed. In PDF by Zaweba ordinary saves work this way, adding only changed objects, which keeps saving quick even for very large documents.

It also matters for signatures. A digital signature covers the document as it was at the moment of signing. Later changes, including further signatures, are added as incremental updates so the earlier signatures stay valid. That is why a contract signed by three people can show three valid signatures. Each one covers its own version.

The side effect is that the old content is still there, and for some purposes that's exactly what you want to see.

What you can do with earlier versions

Each earlier version opens in its own tab, like any other document. You can read it, search it, print it, or compare it with the current version.

That makes several everyday jobs simple. If a form was filled and saved several times, you can see what it said at each stage. If a document was signed and then something was changed, you can open the version that was actually signed. If a colleague edited a report and you want to know what it said before, the earlier version may still be inside the file.

Pairing this with Compare files is especially useful. Open an earlier version, then compare it with the current one, and you get a list of words changed, added and removed, page by page, with formatting and picture changes too.

The privacy side

The same history can give away more than you intended. If you removed a paragraph or a figure and saved normally, the earlier version may still hold it. Anyone with the file and the right tool could open it.

So before sharing a document that has been through edits, deal with the history. Protect, then Remove hidden information lists earlier versions among what the PDF carries, and removes them if you tick that, and Sanitise document removes them with everything else.

If you've redacted anything, removing earlier versions is essential. Otherwise the unredacted text may still be in an earlier version inside the same file.

Signed documents

Take care with signed documents. Each signature covers the version it signed, so stripping out that history can undermine the very thing the signatures prove. If a document's signatures matter, keep the signed file as it is and make any cleaned copy separately.

A quick look before you share

It's worth a quick glance at File, then Earlier versions for any document you didn't create yourself, and any you've edited heavily. If the menu shows several versions, you'll know there's more in the file than the pages suggest. PDF by Zaweba does all of this offline, so you can look into a document's past without sending it anywhere.