In theory it would be possible to convert the files in pdf and then upload them in recall as pdf files, but it'd be clearly straighter and more logical to upload these files in the native extension. Moreover, i think that slides of presentations (powerpoint) and spreadsheets (Excel) should require a different processing: interpreting diagrams in slides, or interpreting and processing computations in a spreadsheet requires a different handling for a valuable "summary" of the document. In Excel there's the feature of pivot tables and charts, and Recall could produce sthg similar with AI.