Introduction: Biomedical PDFs distribute answer evidence across prose, tables, figures, and cross-document relations, complicating the retrieval of answer-sufficient context. We examine whether graph and multimodal retrieval provide complementary answers and whether direct concatenation exploits this complementarity. Methods: We screen 13 local generators on 205 pharmacokinetics/pharmacodynamics multiple-choice questions and evaluate 11 retrieval conditions over ten runs for five selected models. We quantify questions answered correctly by either or both retrieval routes and compare direct fusion with each standalone route using paired question-level bootstrap intervals. A separate ten-run panel tests answer order, irrelevant context, paraphrasing, generated distractors, and option removal. Results: Multimodal retrieval alone answers 11.5–16.2% of questions correctly that graph retrieval misses, while graph retrieval alone answers 7.9–13.9% that multimodal retrieval misses. Counting a question as correct whenever either route succeeds yields an oracle upper bound of 69.5–77.7%, exceeding direct concatenation by 8.4–13.5 percentage points. Direct fusion improves on the stronger standalone route by at most 0.6 points; paired intervals include zero in all ten model–depth comparisons. In repeated evaluation, Gemma-4-31B with multimodal retrieval achieved the highest accuracy (66.6%, 95% CI 65.4–67.8). Discussion: The central finding is substantial answer-level complementarity that direct concatenation does not reliably exploit. The oracle bound measures retrospective selection, not an implemented routing method. These findings motivate evaluating source-aware routing or reranking to select between complementary retrieval routes.