I have a 6-page document with a graphic pulled from a CSV with 51 records that I’ve added to a master page.
If I “Create Merged Document” and put a 1 in “Record Limit per Document,” it works as expected: a separate 6-page InDesign file is created for each record.
If I “Export to PDF” from the Data Merge flyout menu and put a 1 in “Record Limit per Document,” it unexpectedly generates a single 306-page pdf.
I could have sworn that this feature has worked for me before. I also tested this with a 1-page master file with the same combinatorial results, though that’s easier to fix because I can split the PDF into separate pages in the export dialog.