Export to PDF/X-1a:2001 causing errors when the file includes a PDF

[ADKcreative]

I recent designed a magazine for a school, which included a one-page advertisement that was provided to my by the client. When I export the entire magazine file to PDF/X-1a:2001, two lines of text disappear from the ad. But when I export the entire magazine to the Adobe PDF present High Quality Print, the error doesn't happen. 

Looking for insight as to why this is happening. I have always used PDF/X-1a:2001 for file to be professionally printed, and never had a problem. Thanks. 

[Peter Spier]

Perhaps screen shots of correct and incorrect PDFs would help...

[ADKcreative]

Thank you. Here are screenshots... correct and incorrect. Just two lines of text that didn't make it to the final PDF/X-1a: 2001 file. 

[Peter Spier · Accepted solution]

What happens if you export to PDF/X-4?

My gut is telling me this has to do with transparency flattening somehow.

[ADKcreative]

Exporting to PDF/X-4 did the trick. It exported correctly. Thank you!

[Dave Creamer of IDEAS]

And try a PDF/X-3 which won't convert color but will flatten. That would eliminate any color-related issue. Unlikely, I know, but it's worth a test.

Also, check for non-printing layers. I'm assuming the text is one block, but one never knows...

[Mike Witherell]

Have you tried running a deeper Preflight to discover problems about missing embedded fonts?

Have you examined that separate PDF ad in Acrobat Pro fixups?