If they are web applications, there is currently no way to do that.
(Web Intents could have been a way, I think, but I believe it got disabled recently.)
In case your operating system is Chrome OS, you must install an extension (that these web applications may choose to provide, if at all) that registers that web application as a file type handler. Consult your web application support team/forums for more information.
If they are native applications, they must take care of file type associations.
If you are asking about file type associations, this is an operating system feature and this is not the right group for such topics.
☆PhistucK