Why do I always get transparency error when I export to PDF?

Trying to export a odt-document to a pdf file. I want to embed the fonts so I checked the PDF/A-1a box. But then I always get an error message box complaining about PDF/A-transparency. I tried removing potential problems and ended up with an empty document and still got the error box! The file is converted ok but because I want to batch convert loads of odt-files to pdf, the error message box is the only problem. LibreOffice 3.6 and 4.0 behaves in the same way.

I also have this question - what is the solution? I’m using os10.11.2 and LibreO 5.02

The OP does not mention which OS they are using or LO version. The basic problem here is the warning message about transparency, which appears to be a bug. Old closed bug fdo#40618 seems to be the same issue, however I am going to raise a new one (EDIT: fdo#65439) and let the developers sort out whether this is the same issue from back then or not.

As mentioned by @AndersB and @SKelem, for v4.0.3.3 no combination of settings under Tools > Options… > LibreOffice > Print will get rid of this message when exporting to PDF/A-1a. Even a new document containing a single character (e.g., “a”) produces the warning so it is not apparently related to embedded images.

The statement, “I want to embed the fonts so I checked the PDF/A-1a box”, makes no sense as a font subset will be embedded in any PDF exported from Writer.

The last sentence is probably because the OP has read about Word, as the only way to embed fonts there is to check PDF/A compliance.

There are options about print transparencies in:

Menu/Tools/Options/LIbreOffice/Print.

In LibreOffice 4.0.3.3, turning the Printer Warnings settings ON for Transparency, gives a warning when at least one of your images (but they don’t tell which one(s)) has transparency.

If you turn OFF the Printer Warnings for Transparency, then you STILL get a warning when at least one of your images (but they don’t tell which one(s)) has transparency.