Hi David,
We have a new feature to be released with v2.5 that will allow you to enter your contact information in the admin and have it display on the client pages, printable invoices, and PDF invoices. We will send you an email from support with more details about this feature so that you can add it to your system or use it to see a sample of how it's done.
Basically, you can edit the HTML for client pages and the printable invoice page to put your information anywhere on the page. For the PDF invoices, you need to edit the code that generates the PDF.
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Jeremy
DotNetInvoice Support