Altium Outjob Custom Parameters
You can define parameters per Variant as well. I define things like the PCB Number and PCB Revision in the Project Options -> Parameter page, in addition to my contact information, e-mails, etc. This stays static for the given PCB project, and I have a post-processing Python script that can pull out this information to auto-generate documentation.

For the assembled PCBs, i.e., populated with parts, I define different variants, and for each I can define a unique part number, revision, and anything else. These parameters can then be referenced on the schematic, and will be evaluated during OutJob export (i.e. spitting out PDFs).

In the OutJob itself, you can reference parameters while naming the files, which could be helpful to you. For SVN revisions, there might be a Special String field like .VersionControl_ProjFolderRevNumber or .VersionControl_RevNumber, but I think this depends on having Altium's built-in SVN working. And as of the latest version, IIRC, there's not an easy to point to an external SVN binary (like TortoiseSVN), so you could be SOL if you are using SVN+SSH or similar.