Many thanks for your question!
There are two answers here, actually.
First of all, nobody in pdfFiller Team has access to the documents you store inside your account. Our Support and Statistics can see the number of uploads and sendings, but NOT the contents of your documents. That's confidential information.
Regarding your payments details:
If you are paying for our services by a credit card, we see: ***********1234. That is, only the last four digits of your card, the date of transaction and the amount paid.
If you are paying via PayPal, we obviously see the email linked to your PayPal account.
Hope this helps!