I agree with everyone else stating that the digital issues should be a mirror copy of the physical issue. I'm not familiar with PDF, so I'm not sure how you would annotate things and whatnot, but I don't think that's as important as having the digital issue match the physical issue.
Technically and legally digital issues are different publications. They (will) have different ISSN numbers, different UPC numbers, they have slightly different content, different ads, various formats, different article and text arrangement and format, depending on device and even depending on how you hold your device, additional features such as hyperlinks internal and external, zoom into images, slide shows etc, as well as different date of publication.
I think I speak for the majority when I say, with all due respect, that I don't care, and that you're totally missing the point. If the PDF is substantially page-for-page the same as the print magazine to the extent that they resemble one another at a glance, then it should be identical, save for minor minutiae and typographical errors. Just to be clear:
* is it OK if the UPC code is different between the print and digital versions? YES
* if there is a spelling error that went to print, is it OK if the digital version fixes it? YES
* if a picture didn't turn out in print, and the same picture is improved and put in its place? YES
* if a picture didn't turn out in print, and a different picture is substituted in its place? NO
* if somebody didn't pay their ad bill, and it went to print, is it OK to replace it with a different ad for digital version? NO - leave it blank with a placeholder if you absolutely must, we as customers won't like that but we'll understand, but do not publish new content in its place
* if the followup to a story you publish turns out to be more spectacular than what was known when the print version was made, should the digital version be changed reflect it? HELL NO! Add something extra (like an extra page in the PDF or a callout annotation) if that is needed, but DO NOT CHANGE IT, regardless of whether it's a new ISBN, UPC, or whether it's legally OK to.
* if you publish the magazine in a brand new medium (e.g. HTML, iPad) that doesn't preserve a notion of numbered pages like a physical magazine, is it OK to make changes to advertisers, layout, art choices, or to omit some content? for the most part YES, just please don't substantially revise stories.
Digital issues eventually will have content that is not present in printed publication and vice versa. I hope you will not insist on us publishing videos that are present in digital issues, frame by frame in print as well, when at some point we release digital before print?
With all due respect, this is a ridiculous suggestion that clearly demonstrates you're missing the point. No, nobody will insist on this, nor will anyone insist on there being no after-publication extras, as long as they don't replace content that appeared in print. Please sit down and have a meeting amongst yourselves and put on the agenda, WHY DO PEOPLE BUY BITCOIN MAGAZINE, and see if you can come up with any good reasons as to why publishing a manipulated digital edition tarnishes the desirability of the magazine as a whole.