Is there a tool for creating and/or editing PDFs built into FYI?

You can create PDFs in FYI using a template. Refer to Creating PDF Documents from FYI.

You can also use Convert to create a PDF copy of a Word or Excel Spreadsheet document in FYI. This is useful if you want to email the document as a PDF attachment. Refer to Using Convert to Create a PDF in Creating PDF Documents from FYI.

There is no PDF editing tool built into FYI. PDFs can  be edited via your OneDrive using any tool you prefer. Refer to Editing or Printing a PDF.