How can I convert a PDF into an ePub so I can view it in iBooks?

Does anyone know how I can convert a book i found in PDF format to ePub? I tried using a Mac app called calibre and it worked but it didn’t really get the Table of Contents right (by this I mean it added a new interactive table of contents that iBooks all have, which wasn’t very good, and still kept the original text version of the table of contents in the actual epub that was originally in the book sorry if that wasn’t clear), maybe I missed something. Can someone help me please? Thanks!