Hi,look for a company that have scanners,a good ocr software,they usually have a special software for this task.
I hired a company which scanned about, 100000 documents,including books,manuals , letters,brochures, etc.
They were ocred,converted to Pdf format.
Two important issues, define the appropriate resolution, because you may have a very crisp document scanned at 3000 dpi, but its size is maybe 15 mb,while scanned at 200 dpi,maybe is 300 kb,and most of the times 300 dpi,is ok.
Consider that heavy pdfs, will take longer to be read.
Other point,in order to organize the data for an easy sear ching,it is important to define a good structure.
For example it could be,manuals,type,region,speciality ,other, pictures,type,region,zone,etc.
Normally they sell a special software for the management of the data,it is better compared to the option of reading documents by using only the windows explorer and a pdf reader.
Other issue,what are you going to do to ocrscan additional documents,once they left the company, remember that they should be scanned in a similar way to previous, documents,additionally there are out there document management software, with it, you can manage the pdfs as well.
Regards