I'm not sure of the functionality, but are you talking about marking different sections with some sort of auto-numbering and possibly a pre-string label?
So you might have 10 page labels as "i ii, iii, Introduction 1, Introduction 2, 1, 2, 3, 4, 5 for a preface, introduction and main body text.
Somehow, the content would have to be tagged so there is some sort of XML tag that contains the textual content, or a trigger for the start of numbering for each section.
The functionality would be that you would be able to create a PDF in which the 'page labels' would match the actual folio numbers of the pages. So using the same logic that one uses to determine how to print out a correctly formatted folio, one should be able to set a correctly formatted page label. What that logic is might vary a lot - the way a section is numbered is not always to be found in the XML. It might just be that the index section is numbered with roman numerals, or that the second section is numbered in a different way from all the others.
I think what I am trying to say here is this will not always be possible by using just CSS properties (although in many cases it might). There might be some extra logic necessary, so it is important that adding page labels would (also?) be possible through xyPerl
The functionality would be that you would be able to create a PDF in which the 'page labels' would match the actual folio numbers of the pages. So using the same logic that one uses to determine how to print out a correctly formatted folio, one should be able to set a correctly formatted page label. What that logic is might vary a lot - the way a section is numbered is not always to be found in the XML. It might just be that the index section is numbered with roman numerals, or that the second section is numbered in a different way from all the others.
I think what I am trying to say here is this will not always be possible by using just CSS properties (although in many cases it might). There might be some extra logic necessary, so it is important that adding page labels would (also?) be possible through xyPerl