I created a PDF file via Microsoft Visio (a scalable diagramming tool). Later on I decided to make some changes. Visio kinda' sucks, so I decided to swap over and modify it with Adobe Illustrator where it was trivial to blow it up to A3 size and make some necessary changes. The PDF objects are scalable, so there was no loss in resolution, etc. So that was great. I exported in various formats, and all was well. Other revisions were made at different times, but most recently, I can't seem to export the final image without these strange graphical artifacts appearing in the resulting files image.
I'll upload an example when I get the chance, but they're little white and grey squares with a kind of cascading staircase pattern if you look closely.
I don't believe I've done anything differently, but I can't seem to get rid of them. They're not displayed in the image within Illustrator, only in the resulting files. There seems to be one for each Visio object. Any idea what they are, or how to suppress them?