If you are designing your ad in Indesign, it’s pretty simple. You set up your document as a 8.25 x 10.875 page and set the bleed to .125”. Then when you "Show Guides" in the document you’ll see exactly where the trim lines, bleed lines, and margin lines are.
When exporting to PDF from Indesign, you should use the PDF/X-1a:2001 preset and UNCHECK all marks, but INCLUDE .125” bleeds.
If you are building your ad in Photoshop, you need to create a Photoshop document that is 8.5” x 11.125” @300dpi (assuming full page ad) then manually add guides at .125” in from all four sides so they can see where the page will trim. Then from those guides you need create another 4 guides .25” in from those to show the margins (safety area). See screenshot:
If building in Illustrator, set-up is similar to Indesign. Create the artboard at the actual size and add the .125” bleed which will automatically show the guides in the document. You will have to manually add margins guides .25” in from the artboard edges. When saving Illustrator .ai files to Adobe PDF file, and also use the PDF/X-1a:2001 preset, UNCHECK all marks, INCLUDE the .125” bleed.
Contact Jamie Bogner (firstname.lastname@example.org) if you have any additional questions.