In order to enable uploading of large files via IIS (Microsoft Internet Information Services) the request filtering of jakarta and the website has to be adjusted. Open IIS manager, browse to jakarta and double-click the button Request Filtering. Press Edit Feature Settings... and change the value of the Maximum allowed content length (Bytes) to the desired size (e.g. 52428800 = 50 MB). Repeat this step on website level and restart IIS afterwards.
IIS request filtering
Adjust maximum allowed content length (Bytes)
Note: This setting is important if you are using WebOffice10.8-DVD\Software\Miscellaneous\Apache Tomcat Connectors\ApacheConnector_Tomcat90.zip since your file traffic is redirected to the IIS instead of using Apache Tomcat.