Little white lines. I've never had a problem printing a PDF that had those little white grid lines in it but now I am using the same InDesign file to also create a digital issue and the white lines are beyond my brain's toolkit. They won't show up in the iPad version but they will on android or vice versa. Sometimes a background will drop completely out of an ad that has behaved all the way to the end. I must be missing some step - some flattening or rasterizing or standing on my head step. Here are the PDF settings I'm using for my digital PDF: Standard: None; Compatibility: Acrobat 6 (PDF 1.5); Optimize for Fast Web View is checked; I've got Image Quality set to maximum on the compression page and Monochrome at 1200 so the text stays clear when you zoom in. Once I process the PDF it goes to my boss who runs it through INHouse Digital Publishing app. It's at that point that ad backgrounds will drop out or misbehave. Any advice is most welcome!! Please help!
I most strongly suspect that your “INHouse Digital Publishing app” is flattening any and all transparency in your PDF file causing flattening artifacts.