Of course one can merge two or more pdf files into one. Create new project: Drag/drop or place pdf one onto page
Select on the toolbar which page to show on this page
Duplicate page and choose another page from the toolbar to show on this second page etc.etc.

Drag/drop or place pdf two onto a new page 
Select on the toolbar which page to show on this page
Duplicate page and choose other page from the toolbar to show on this second page etc.etc.