Open up Fluid PDF with a loaded document. Click Sign>Template Design as shown below:
Click Templates->New Template and open a typical sample pdf document. You can enter an unique meaningful Template Name. Then click Regular Expression.
Choose a identify file name method as shown below: Prefix, Suffix, Contains or Custom.
Enter the text pattern which corresponds to the file name method.
It will generate into a regular expression and you can click Save.
Once Saved, you can click Place Field. Subsequently, you can drag and drop a blank signature field onto the document. The coordinates of the blank signature field is recorded on the left panel.
Click Save to record this template. Click Mode to edit the signature field size or location. Otherwise click Close if you want to finish.