How to compare two versions of a Word document

In Microsoft Word

Open Review → Compare → Compare. Pick the original under Original document and the edited copy under Revised document. Word writes the result into a new document, with every difference shown as a tracked change in the name you give under "Label changes with".

Click More to choose what counts as a change. Formatting, case changes, white space, tables, headers and footers, comments and moves can each be left out, and you can compare word by word or character by character. Leaving formatting out is the quickest way to cut the noise when someone has only fixed the wording.

Combine, next to Compare, is a different tool. It merges the tracked changes from several reviewers into one document, so use it when people each edited a copy with tracking on.

In LibreOffice Writer

Open the newer version, then Edit → Track Changes → Compare Document and pick the older file. Writer marks the differences in the document you have open, and Edit → Track Changes → Manage lists them to accept or reject one by one or all at once.

Writer compares paragraph by paragraph and then word by word inside a changed paragraph. A heavily rewritten paragraph can come out as one deletion and one insertion, which is accurate but less helpful to read.

In Google Docs

Open one version and use Tools → Compare documents, then pick the other from your Drive. Google makes a third document with the differences as suggestions, credited to whoever you name. A .docx has to be converted to a Google Doc first, so check headers, footnotes and tables afterwards, because those are where conversion loses things.

Getting a clean comparison

• Compare against the exact file you sent, not a later copy of your own. Otherwise your edits and theirs get mixed together.
• Accept or reject the tracked changes in each version before you compare. A comparison of two documents that are each full of revisions is very hard to read.
• Save both as .docx first if one of them is an old .doc or a PDF. For two PDFs, Adobe Acrobat Pro has its own Compare Files tool, though text pulled out of a PDF compares less cleanly than a real document.
• Keep the comparison as its own file. It is a record of what changed, and you can still accept everything to end up with the edited version.