I think there are some good UiPath components you can leverage to do this.
First, in your “Snippets” menu, you should have the file “For Each File In Folder.xaml”. This workflow iterates over each file in an indicated folder, you can either build on top of the snippet or use it as a model to build something similar.
Having this component, you need to write some logic inside the for loop. For each file you could start by checking that it is a PDF by looking at the filename. Then, you could send the file with one of our “Send Mail” activities (there are a few, you need to choose one based on your email provider). Lastly, you can use a “Move File” Activity to move the file after you’ve emailed it. Writing this all in the “for” loop will apply it to each file one at a time.
Hope this helps!