Setting "Author" for multiple records?

I have a database of 1400 presidential speeches and I’ve found that editing the “Author” field of “Document Properties” to be a handy way of quickly sorting by president. The problem is that I have the Author set for only about 10% of the records. I’d like a way to set the Author field in batches. I know which records are which, so it’s not a matter of accidentally setting a field with the wrong Author (even if it was, I could correct it). So far, I’m not seeing a script or dialog option to accomplish this, and trying to edit the field with multiple records selected does not work. Any suggestions?

EDIT: If the Author field isn’t going to be manipulable (?) the way I want, I’m also willing to use a different field (as long as it’s logical) if it will allow the sort of batch editing I’m looking for. Tags will not work, however, since I cannot create a Smart Group field that will allow Boolean logic in the tag matching field.

Changing the PDF metadata – which includes the “Author” field – is possible but would require a custom AppleScript or higher-level language. (However, I don’t believe this is yet possible with DEVONthink scripting.)

For an alternative, why not append a prefix (a code or name) to the document names? There is Scripts > Rename > Add Prefix, for example, that works on multiple selected documents.

These are actually text documents (RTF), but I assume the same issue applies? As for prefixing the name, I was hoping to avoid this, but if that’s only practical solution at the moment, so be it.

Sorry, I always assume PDFs when not specified. (Plain text does not have editable metadata; RTF does.)

Yes. Same issue.