Kevin Fulton wrote:
It's possible that the client wants you to follow the page numbering of the original document, but if all the text doesn't fit, number that extra page 1a, 3a, etc. rather than numbering it 2.
I don't work with translation software, but in my experience as an editor with publishing houses (esp. long ago, when everything was in hard copy), if a change is made that would have required repaginating the entire document, the editor would instead simply insert a page after the page where the change occurred. So, if the change was made on p. 11 (for example), then there would be p. 11, and a new p. 11a (which might only contain a word or two).