This has just solved the same problem for me. I guess the go to answer is set all scenes in Sketchup and do not alter in Layout (until the pdf ‘fade’ glitch is fixed at least). That’s just taken an hour of scrolling through help documents and downloading acrobat reader etc etc etc before I found your suggestion - thank you! (for added info, I just used the context menu over the image to set the viewport to another scene and then back again to the one I want as a sort of reset of the view - I hope that makes sense!). One more thing to add, in ‘document set up’ under file menu, set the resolution to high then, before printing, hit save. No idea why the save is important but its seems to make a difference.