I highly doubt it there is such a solution as it would require Crystal Reports to generate a LiveCycle or Acrobat PDF output which I am sure it isn't capable of doing.
One way you might be able to easily achieve your conversion is to export your existing contracts to PDF (generate the report in CrystalReports and export to PDF), then use LiveCycle Designer ES to import that PDF. You have two options for importing - the first option essentially imports the document as a background image and you trace fields over the top, the second option actually imports the document itself and tries its best to identity fields, text and lines. You only really need the second option if you are planning to make the PDF interactive and dynamic (show / hide fields based on user input).
Once this is done, you can add your digitial signature to the form.
Hope this helps,
John.