If you are using IIS for hosting Staff.Wiki, then the default maximum upload file size is 4MB. If you are uploading videos or large PDF files, for example, you will need to increase it.

To increase it, please use this below section in your web.config (found in your Staff.Wiki installation folder):

<configuration> 
   <system.web>
      <httpRuntime maxRequestLength="1048576" />
   </system.web>
</configuration> 

For IIS7 and above, you also need to add the lines below:

<system.webServer>
  <security>
     <requestFiltering>
         <requestLimits maxAllowedContentLength="1073741824" />
     </requestFiltering>
  </security> 
</system.webServer> 

Note: maxRequestLength is measured in kilobytes. maxAllowedContentLength is measured in bytes. This is why the values differ in this config example. (Both are equivalent to 1 GB.)