Custom button assign

Greetings.

I’m part of the Development Team of https://tax.weil.com/ . We are studying the possibility of use your “Print friendly and PDF” WordPress plug-in. But we have some questions to make:
1) If you check the posts on the blog (link above) we have our own custom button for PDF, Print & Email. We need a walkthrough guide to assign “Print Friendly & PDF plugin” on our custom button and directly downloading PDF without opening print friendly in a new tab/window to download PDF or Print.
2) We also have our own custom CSS which is applied currently on print view, Can we give reference to print css file within plugin to keep design for Print/Pdf same as existing site Print view.

The page I need help with: [log in to see the link]