My custom control uses the gambas pdf component
If the pdf component is NOT included in an application that uses my custom control then I get an error:-

Cannot load class 'PdfDocument': Unable to load class file

Am I missing something or is this the way it's supposed to be?

Take a look under point #2 under introduction:

/dev/gambas - Gambas Documentation

Thanks jornmo, I already have gb.pdf required.

 Thought I may have been using an earlier version of the control, so have double checked.  The version is the latest.
Attached is an image of my properties/information tab - is this correct?

(Click to enlarge)

That looks right to me. How du you use it in your app? Did you make an intallation package of it, and install it on your system?

 Yes, I'm using Kubuntu 18.04, Gambas 3.12.2.