The most obvious choice for pdf to gpx conversion is recovery of GPS data from exported PDF files. To achieve this, you will need a dedicated GPS tool - for example MyGeodata Cloud.
Another, completely different, conversion of pdf to gpx is related to Guitar Pro software that also uses .gpx files. Whilst Guitar Pro can export .gpx music sheets as PDF documents, it does unfortunately not work the other way. It is unlikely you can achieve this this conversion directly, however some programs claim to allow conversion of music sheets in PDF formats to MusicXML format which you could import to Guitar Pro. We couldn't verify this piece of info though.Open PDF file Open GPX file
An online GIS converter