Use Save As or Export. Avoid Print To, if you can!
On a MAC, make sure you also check the printing settings as those sometimes interfere with how the file is exported to PDF format.
From Adobe Illustrator
Create a bottom layer with a white rectangle, then export to PDF.
(If the poster was designed in Illustrator without a white rectangle as the bottom layer it will automatically save as a transparent background. This will crop your poster to the closest object getting rid of any margins you may have. Placing a white rectangle as the bottom layer preserves the margins and dimensions of your poster.)
Export your file using XeLaTeX, not the default PDF LaTeX (Menu → Settings → Compiler). If using Overleaf, make sure to clear the cache as well.
Open the PDF and check that all the information has transferred properly before submitting your print order!
Borders Around Graphics
Sometimes during exporting to PDF, weird borders appear around graphs and charts that are not visible in PowerPoint. While we don't know the precise cause of this, and we have no sure fix for it, we have seen various degrees of success with the following solutions:
Save in a different PDF setting, if PowerPoint gives you the option (Please note that you may have to try different options, not necessarily the one pictured)
If you used any PNG files in your PowerPoint, convert them all to JPG/JPEG and re-insert them onto the PowerPoint file, then re-export.
Export the ppt slide as a JPG/JPEG. This one is tricky - you need to pay extra attention to the size, graphics, and pixelation when exporting as JPG.