When working on a joint project, my collaborators and I encountered that we obtain significantly different PDF outputs with the same latex source. To be more specific, this already happens with the example .tex (and .sty) files for this year's NeurIPS 2021 conference: https://neurips.cc/Conferences/2021/PaperInformation/StyleFiles. When compiling the example .tex file on Overleaf, I obtain exactly the same pdf output as provided by the organizers, with a length of 5.5 pages (https://media.neurips.cc/Conferences/NeurIPS2021/Styles/neurips_2021.pdf). When compiling the same file (with the same style file) on my local system, the result is half a page longer, filling the complete 6 pages.
Here are some observations: Line breaks seem to happen at the same places. Instead all the vertical spaces seem to be a little bit larger in the file compiled on my own system. There is not a specific object that needs more space. Instead, it looks like every single line needs a bit more space. However, the font size itself is identical. Also the textwidth and textheight, as well as, the paper measures (letterpaper) seem to be the same.
Even switching between MikTex and TexLive on my local system does not solve the problem.
Since NeurIPS has strict page limits, it makes a crucial difference whether a file is half a page longer or not.
Any help is highly appreciated! Thanks!