CastleCMS DocumentViewer
CastleCMS has default document viewer capability for most 'Office' file types including .xls/x , .doc/x , .ppt/x and PDF
See an example below of a 'non-searchable' PDF made searchable from the 2019 report about the Russian Interference in the 2016 Presidential Campaign. This PDF was originally a printed copy (or the like) scanned on a Xerox copier. CastleCMS Document Viewer, Optically Character Recognized the file and saved it, and indexed it for search. Native Functionality to this CMS!