Starting now, all single-page PDFs generated by CalTopo are Geospatial PDFs. Edit: Looks like I jumped the gun a bit. There were some compatibility issues with the iOS version of Avenza that have now been fixed.
Complementing this is a new short-URL feature that makes it easier to share CalTopo PDFs or load them onto a phone. Step 1 is, as usual, to click Print and then Create a PDF:
Anyone with this URL can now download your PDF; no need to save it to a computer and then share using a 3rd part hosting service. While the print page indicates that links expire in 30 days, I may keep them around longer if they don't occupy too much space - currently I have to go in and purge them manually.
The only reason for a separate Generate Link button is to avoid cluttering my database with PDFs that will never be shared. If that proves to be a non-issue, I'll merge them into one button that always generates a short URL.
I have no affiliation with Avenza, but their free PDF Maps app allows you to import directly from the CalTopo URL: