What Free includes, and when Pro is worth it
Free is 12 commercial invoices a month. Pro removes that cap. Estimates, clients, and reports are on both.

Free
Twelve commercial invoices each calendar month. The A4 PDF, the share link, and bank details per currency are included. Clients, estimates, bills, and reports do not count toward the 12.
Pro
USD 9.99 a month, or USD 99 a year. No monthly cap on commercial invoices. A public address such as yourname.wireinvoice.com is included. You pay on the site. Cancel from the billing page. Pro stays until the period ends.
What does not change
The invoice your client receives is the same on both plans. Pro is for volume, not for a different document. Wire Invoice still does not hold the payment.