The purpose of this study is to compare the efficacy and safety of PEGylated Recombinant Human Hyaluronidase (PEGPH20) combined with nab-paclitaxel plus gemcitabine (PAG treatment), compared with placebo combined with nab-paclitaxel plus gemcitabine (AG treatment), in participants with hyaluronan (HA)-high Stage IV previously untreated pancreatic ductal adenocarcinoma (PDA). Participants will be randomized in a 2:1 ratio to PAG or AG treatment.