I tried to integrate both libre office (V6.0, V5.4) and open office (V4.1) with Liferay 7 GA5 and in all cases pdf doesn't include images. I tried both pdf generation from web content display portlet and custom pdf generation (by using Liferay API).

The conversion process (e.g. LibreOffice) would request images just as a browser would. That means that the Libre Office (and hardware it's running on) must have access to the webserver (Liferay). Typically both are on the same computer, and there might be weird DNS-resolution and firewall rules for the public address availability. Or read-protected images (LibreOffice connects as guest).

Hi Alex Wom. It's been a long time, but did you find a solution for integrating LibreOffice with Liferay? I also have a problem with displaying images in generated PDF.