I've been getting sexual in my text that went directly into my PDF folder and I had to delete one at a time from my folder. What a pain that was as they would mix in with my legitimate PDF's. If they have your email address they can send text or PDF. No blocking option on my phone for PDF's. They still came through. I deleted them as I got them and they finally got bored and stopped sending them. Remember, your email address is also your text and PDF address like mine is Gmail. My PDF files were sexual and I had to click on a link to open them. I simply didn't click on them but they were filling up my PDF folder in my drive. I had to download PDF READER to gain access to them and delete them from there one at a time.
I understand how frustrating this is. You can block and delete unwanted messages. When you get a sketchy text, select Block number at the top of the conversation. To view blocked numbers and messages, or to block a number, go to the Conversations tab, tap More options (the three vertical dots), and then tap Settings. Tap Block numbers and messages. https://www.samsung.com/us/support/answer/ANS00062352/
