Are there different series or editions of Doraemon comics available in PDF format, like the original manga vs. spin-offs?

Yes, there are several different series and editions. The primary collection is the original Doraemon manga by Fujiko F. Fujio. Beyond that, you might find PDF versions of 'Doraemon's Long Adventures' (feature-length stories), 'Doraemon Plus' (extra volumes), 'The Doraemons' (a spin-off series), and various educational or themed comics featuring Doraemon. Availability in PDF format will vary by region and publisher for each specific series.