You can use the Text Processing extension on Marketplace.
> Import data (PDF file) using "read document" (you can use "loop files" and insert the "read doc" operator inside to read all pdf files there) then you can use the "process document" to treat your text(s) and in the end, you can use "wordlist to data" and run with the "EXA" port connected. So you go to Results View and choose a visualization on left and choose Word Cloud. At least I think it can help now, but you can improve this process as you like/need
Answers
> Import data (PDF file) using "read document" (you can use "loop files" and insert the "read doc" operator inside to read all pdf files there)
then you can use the "process document" to treat your text(s) and in the end, you can use "wordlist to data" and run with the "EXA" port connected. So you go to Results View and choose a visualization on left and choose Word Cloud. At least I think it can help now, but you can improve this process as you like/need
Please take a look into the text mining tutorial and make sure you install the text minning extension.
https://academy.rapidminer.com/learn/course/text-and-web-mining-with-rapidminer/text-and-web-mining/lets-get-started?page=1
This is an example that might help you.