I think it depends on the scale you want to do this on.
Some options from small scale to large scale:
- Let the user save the excel as pdf and upload the pdf, then merge using CommunityCommons.
- Let the user upload the excel, then do an excel import and create a PDF using Mendix templates.
- Let the user do an upload, then convert using an external service or java library. Apache POI is a possibility, there are marketplace modules available for PDF generation. Aspose offers enterprise quality PDF creation and document conversion. You could use that, but that comes at a price.
These were some options that came to mind, there are always more possibilities.
I hope this helps.