Leo,
The keys part of the request are using GDC and to display PDF inside a GDC Window.
As I understand it the rendering engine of the WebComponent does not have the appropriate plugins to render a PDF document inside a WebComponent. The acid test I use with each GDC version is to try something like ...
DISPLAY "http://4js.com/mirror/documentation.php?s=genero&f=fjs-genero-3.00.XX-PlatformsDb.pdf" TO browser
... hence the use of solutions involving pdf.js
At the moment, my suggestion would be to use a 3rd party tool such as imageMagick to convert a pdf to an image file for each page and display the image file. In Genero 3.10, instead of imageMagick you can use Genero Report Writer to create an image for each page of the PDF. I have put my sample that does this up here
https://github.com/FourjsGenero/ex_embeddedpdfviewer, unfortunately there is an issue where I get black background instead of white in most circumstances
https://github.com/FourjsGenero/ex_embeddedpdfviewer/issues/2 which I have reported internally and will hopefully be resolved before 3.10 is released next month.
Ideally though the WebComponent engine would have a PDF Viewer plug in built in so that PDF Documents could be rendered inside a Genero form rather than outside in Adobe.
Reuben