There are no limitation to the uploaded file size in Headwind MDM.
However there may be limits on the reverse proxy if you're using it, or on a firewall.
If you're getting the upload issue, consider using external file storages (you can specify the external URL for the application instead of uploading an APK file). Also, you may need to update Tomcat as described here:
https://qa.h-mdm.com/16889/