What usually happens if the typesetting process for a paper puts it overlength? I imagine if the conference has an extra page charge, this will be applied; but if the conference has a hard maximum limit for pages and the paper is squeezed to fit it, and the typesetter makes some formatting changes that puts it over the limit, what happens?
Will the conference allow the author to make some adjustments to fit the paper into the limit? Assuming the formatting issues were an honest overlook and not purposely trying to circumvent the limit!
In my experience, my co-authors and I typeset articles ourselves using a template provided or referenced by the conference and submitted in PDF or PDF plus source form if the source is LaTeX. Overlong papers are often rejected by the Program Committee before being sent out for review or are asked to be reduced in length to meet the standards. If the paper is to be typeset by a publisher after the conference for a proceedings volume, there may be some wiggle room, but not much.
One goal is to not allow the authors to make substantial changes after the deadline. PCs have to be careful about allowing one group of authors to make too many changes after the deadline because they were overlong. This isn't fair to others authors, and so many PCs are strict about length restrictions.