I had a problem with the last step: The docu says:
20. From the Server Behaviors panel, double-click on the Update Record option.
21. Click Next to proceed to step 2.
22. Select the column you applied the file field to.
23. Click the value lightning bolt.
24. Expand the WA Upload File option for your column.
25. Choose Server File Name.
In my case 24. is called:
WA Upload Files (name_of_form_field)
mind, there is also another one called
WA Upload Files Global Status (which would be the wrong choice)
And there is an ongoing focus problem which only happens with WebAssist Extensions (Windows 7 / CS3).
According to the same description further up:
15. Choose the Default file value lightning bolt.
16. Expand the WADAUpdateForm option.
17. Choose the form field you set to hidden earlier.
18. Click OK.
in 17. I chose the Default file as described. Later I checked the code and found:
'DefaultFileName' => "",
So, it did not accept the choice,
a choice that I had to put manually after I found that it did not work:
'DefaultFileName' => "".((isset($_POST["field_name"]))?$_POST["field_name"]:"") ."",
This never happens in Dreamweaver's entry fields i.e. Server Behaviours like in "Recordset" or those of any other Extension producer.