When using pdf export to convert a PDF into Excel spreadsheet the info appears as symbols

I am new to the product of PDF Export but I am trying to convert pdf documents that have been emailed to me into a spreadsheet like Excel.  The PDFs I have received come from several sources so the layouts are different.  I have noticed that I am getting some that convert just fine and others that dont. For the PDF docs that dont convert over the number values in the PDF show up as symbols on the Excel doc. I was wondering if anyone had any suggestions on how to correct this so that the conversion works.  I dont receive error messages during the conversion just an Excel doc that is unreadable