The normal practice when you make direct quotes, is the reference page of the edition one is using. And has been for a good time. In reality, this is not a system very suitable.
First in relation to the texts that have multiple editions (what corresponds to page 200 of my edition in another edition?). In some texts of philosophy -at least in my copies of the Critique of Pure Reason and The Ethics of Spinoza – appear in the margins references to the pagination of the first edition (and in the case of the Critical pages of the first two editions). In any case, it is not something standard -and not what I have seen in multiple texts that have various editions. The problem remains, therefore, in general existing.
Second, in relation to the texts in digital editions (no digital files, the PDF is usually the same as the print) that do not necessarily have paging. In the case of Amazon with Kindle there are several texts that include in addition to paging, but it is not necessarily accurate (the point where the change of page is not clear, what for the purposes of appointment is problematic). But again, not all the texts have it. And finally, the reference to the pagination is a particular issue, with which we return, in the best of cases, the problem mentioned in the previous paragraph.
Perhaps the best thing, then, is simply to return to the system that was (and is) common to refer to classical texts: Since there are multiple editions and translations, and given that they were written before the printing press, the use of pages it is rather inconducente. For some cases, there are specific systems that standardize the reference (Bekker in the case of Aristotle, Stephanus, in the case of Plato), but many times we tend to use the structure of the text (book, paragraph). Given that the structure is unchanged through the various editions, all over the world -regardless of the edition – know what you’re referring to.
Then, and even just end up being a use idiosyncratic, that is the system that I will use henceforth for all my appointments (I hope that they accept it in the thesis of doctorate). The only exceptions will be direct quotes, to journal articles -given that they only have one edition finally. And so I control and command you.