Yes, you may use your credit card without having to open an account with PayPal.  The process is easy and very quick.  Whether you use your credit card or your PayPal account, all information is processed on a secure server where your personal information and payment is protected.

The images below are actual screenshots from the PayPal web site.

When you click on any of the payment buttons to purchase diagrams, you are automatically redirected to the PayPal's secure payment page (note the "https://" in the web page's URL) where you may either pay by credit card or your PayPal account.  If your are making payment by credit card, click on the Continue link. 

When you click on Continue, a screen will appear where you may enter your credit card information.

After entering your credit card information, click on the Review Order and Continue button.  After your credit card purchase is approved, a screen like the one below will appear.  After reviewing the information, click on the button IMPORTANT: Click here to download your product.  When clicked, you will be redirected to a web page that gives information concerning your user name, password and instructions how to access your diagrams.  Whether you click on the button or not, you will receive an e-mail in a few minutes with the same information.

If you need further assistance, please e-mail me and I will help.