Heya, welcome to MR.
I am no expert with PDF conversion - there are a ton of people who can help for sure though, including using the excellent calibre.
One other thing to try though - which Kindle do you have? You can use the free Kindle email conversion service to convert a variety of non-DRM'd formats to the AZW/mobi format Kindle uses.
insert your Kindle/Amazon email account username firstname.lastname@example.org
Attach the PDF and email it. Amazon will autoconvert and email you back to the account have registered with them.