Validating the poster files can only be done by the individual speakers. Please check the PDF requirements in advance. For more information, see: What requirements does a PDF poster need to meet to be correctly displayed?
The easiest way to check if your poster displays properly is to open the PDF with Mozilla Firefox's browser. Firefox's default display plugin is very similar to the PDF viewer that Converia Virtual Venue uses and therefore is a good indication that your poster will be displayed correctly.