Found 3 examples (to View, scroll, Zoom, Fill, Weblink, Read, Save pdf form).
It was from kjteng, whch has 4 examples (I could not get example 2 to work):
PDF VCL Control using PDFium
https://github.com/kjteng/PdfiumLibSome extra files from that Github page:
A pdflib.dpk file (and also Tpdfcontrol.lrs) is also included for those who wish to place the TPdfControl to the component palette in Lazarus. Before installing the dpk, please remember to uncomment the line containing {$DEFINE VCL_PALETTE} in pdfiumctrl.pas. You may also need to delete the files in project\lib\ folder to ensure a clean start. The Example1 (PdfiumLibExample) is also originated from Andreas Hausladen's site, with some minor modification for Lazarus.