A Study to Compare Upadacitinib (ABT-494) to Placebo in Adults With Rheumatoid Arthritis (RA) Who Are on a Stable Dose of Conventional Synthetic Disease-Modifying Anti-Rheumatic Drugs (csDMARDs) and Have an Inadequate Response to csDMARDs

* Diagnosis of rheumatoid arthritis (RA) for \>= 3 months who also fulfill the 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) classification criteria for RA. * Subjects have been receiving conventional synthetic disease-modifying anti-rheumatic drug (csDMARD) therapy \>= 3 months and on a stable dose for \>= 4 weeks prior to the first dose of study drug. * Subject has \>= 6 swollen joints (based on 66 joint counts) and \>= 6 tender joints (based on 68 joint counts) at Screening and Baseline Visits. * Subjects with prior exposure to at most one biological disease-modifying anti-rheumatic drug (bDMARD) may be enrolled (up to 20% of total number of subjects) after the required washout period. Specifically, prior to enrollment: 1. Subjects with limited exposure to bDMARD (\< 3 months) OR 2. Subjects who are responding to bDMARD therapy but had to discontinue due to intolerability (regardless of treatment duration).

* Prior exposure to any Janus kinase (JAK) inhibitor * Subjects who are considered inadequate responders (lack of efficacy) to bDMARD therapy, after minimum 3 months treatment, as determined by the Investigator. * History of any arthritis with onset prior to age 17 years or current diagnosis of inflammatory joint disease other than RA (including but not limited to gout, systemic lupus erythematosus, psoriatic arthritis, axial spondyloarthritis \[SpA\] including ankylosing spondylitis and non-radiographic axial SpA, reactive arthritis, overlap connective tissue diseases, scleroderma, polymyositis, dermatomyositis, fibromyalgia \[currently with active symptoms\]). Current diagnosis of secondary Sjogren's Syndrome is permitted.