using custom template for a Document Library in SharePoint 3.0

Is it possible to use a pdf file as template for a Document Library in WSS 3.0?
First I uploaded a blank pdf file to the forms folder of the document library.Then I tried several times to set this file as the template for a new document library but when I specify the upoaded pdf file name as template url(relative to the site), I get an error message ‘Invalid url’. Why does this happen?