A 46-year-old man presents to the emergency department with acute onset pleuritic chest pain and dyspnoea. He returned from a long-haul flight 5 days ago. He has a swollen, tender left calf. Vital signs: blood pressure 118/72 mm Hg, heart rate 112 beats/min, respiratory rate 24 breaths/min, oxygen saturation 92 percent on room air. CT pulmonary angiography confirms multiple segmental pulmonary emboli. He has no active cancer, no renal impairment, and no recent bleeding. According to Canadian thrombosis guidance, what is the most appropriate initial outpatient anticoagulant choice?