You can control the visiblilty of the submit button by getting another field to link to the submit button and then changing that other fields visibility. Because these two fields are linked they will have the same visibility. 

 
 

e.g :  

add a explanation field and then change its reference to //SYS_ACTIONS/SYS_SUBMIT_DOCUMENT

 
 

 
 

 
 

 Doing this will link the explanation field (it could be any field) to the submit button, now whatever we do to the explanation field it will have the same effect on the submit button, so, lets make the explanation field read only using a formula, see further below: 

 
 

 
 

 
 

 
 

As you can see button is disabled (you can also hide it)  

 
 

 
 

 
 

Formula in the explanation field