hi
in the screenshot i see the print preview, not a pdf viewer...
the print preview has not much to do with what you will get in a pdf... and might or not reflect what you will get at the end. (and, yes, it should show exactly the same content, but this is not really very helpful for you, if you have a workflow based on PDFs: most of all, depending on the PDF options, your document might be rendered with some differences).
can you share a .sla showing the issue?
ciao
a.l.e