This is a Phase 3, randomized, double-blind, placebo-controlled, efficacy and safety study of subjects with IPF treated with inhaled treprostinil over a 52-week period. Prospective subjects will be assessed during the Screening and Baseline Visits to determine eligibility for the study. Screening activities may occur up to 45 days before Baseline. At the start of Screening, subjects will sign the informed consent form (ICF), then undergo assessments. Eligible subjects must have a diagnosis of IPF based on the 2018 ATS/ERS/JRS/ALAT Clinical Practice Guideline (Raghu 2018) and confirmed by central review of HRCT imaging (performed within the previous 12 months) and surgical lung biopsy, if available. Confirmation that a subject qualifies must be received before the Baseline Visit and randomization.