Allow to combine files in the software and don't send users to a website.
Few times I've been able to combine files into PDF without having to use a web based service. Why I can't do it anymore? I tried to disconnect from the internet to see if it will force Acrobat Reader DC to work, but it was sending me again to this website. This is an accessibility issue. Secondary, I already have the files on my computer - why should I upload them somewhere and then download again?! Why install Acrobat Reader DC if it just sends me to a website? Please, invest in some UX exports and do some user tests on those flows.