GoodReader (iOS)
Used by 8 peoplegoodreader.com ↗

“GoodReader: my favourite PDF reader on the iPad, especially since it can sync PDFs with my NAS.”
Ludovic Chabant Interview, Software developer (Epic) · via Uses This 
“On my iPad the most important app is GoodReader.”
Chanda Prescod-Weinstein Interview, Theoretical cosmologist · via Uses This 