How can customers pay me with PayPal?

You'll need to have a PayPal account for this to work. To create a PayPal account to go https://www.paypal.com/

Your customer will see a link on the bottom of the invoice they receive by email. When they click on the link, they will need to login to their PayPal account to complete the payment. If you have a Business PayPal account, your customer can also pay by credit card through PayPal even if they don't have a PayPal account.

Mobile

1. Open the Settings menu by tapping the Settings icon.
2. Tap Preferences.
3. Enter the email address associated with your PayPal account.
4. Tap Save to apply the change. (Street Invoice will now synchronize with the server). 

A link to PayPal will now appear in invoice emails. The payment amount will be set for the full balance of the invoice. More options are available on the Windows version.

Windows PC

1. Click Settings
2. Click Payment Gateways
3. Click New, and enter the email address associated with your PayPal account under Email Account
4. Select where you'd like the link to appear, and the payment amount. For Invoices, you can choose either the Amount Due on this invoice, or the customer's entire balance due. For Statements, you can choose the Amount that is past due, or the customer's entire balance due.