You can.
I copied and pasted this from a site I found. It explains it.
To add a credit card to a PayPal account, simply go to your Profile after logging in and select Credit Card. You can also mouse over the word Profile and choose Add or Edit Credit Card right from your Account Overview screen. As you approach your account's limit, you will be prompted.
If you plan on spending more than your account's limit with PayPal in the long term, please note that it doesn't have to be your personal bank account on file with us. If you have a separate bank account, possibly for business or savings, PayPal does not require you to keep a minimum monthly balance in the account. Rather, although we don't know all of the information that a bank asks of you to qualify for an account, by you registering a bank account with us and informing us of two small deposit amounts that we send to the account, we know that the person who signed up for the PayPal account has access to the financial instrument on file.