Preserve authentic records and add an accurate explanation of changed names or systems. Do not alter their original meaning to make the history appear simpler.
Explain the relationship between records
Identify dates, authors and the applicant’s contribution. Ask an appropriate company record holder to explain technical continuity where relevant. Mark uncertain links for review rather than presenting them as established facts.
Rewriting is almost always well-intentioned and it is the thing that does the damage. Someone opens a decade-old training certificate, replaces the discontinued product name with the current one so the file reads consistently, and has now produced a document that no longer matches the issuer's own records. If anyone checks, the inconsistency is worse than the one it was meant to remove.
Keep the original exactly as issued and put the explanation beside it: a short signed note from the person or department that can attest to the renaming, giving the date it took effect and what did and did not change technically. Name that attestor. An unsourced note explaining a name change carries no more weight than the confusion it addresses, and a reviewer will ask who wrote it.
Where the issuer no longer exists, say that too, and identify whatever secondary record survives. Scan the originals before anyone edits a copy, so the unedited version still exists.