How to revert to old acrobat? How to send an E-sign template with additional attachments?

OK - so it was changed again, and looks permanent as I cannot find a way to get the old esign back?

I have dozens of templates that I use to send out to my clients, and then I attach their documents to the templates as well. The new system (and it did this two years ago when it "upgraded" to the new interface) will not allow me to add an attachment like i could before - 

I get a note saying it cannot process the files - error 

HOW can i make this work? I am beyond frustrated and I send out 5-10 contracts a day!!

Unable to process files

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