[carlosjobim]

No, you haven't done anything wrong. Some people are just paranoid-compliant to the maximum level. Unless a company is doing actual money laundering or financing terrorists, the tax auditors won't give a damn about some wrongly formatted invoices from freelancers, as long as they are based on reality.

[solardev]

Ok, phew, thanks for the reality check! We don't finance any terrorism (unless you count the quality of my code). We're just a small company without a big legal/accounting dept.

[throwaway11205]

PDF invoices are nothing wrong. As long as you're not a VAT payer there are just basic requirements (vendor/customer ID and address, invoice number). Most likely yours is compliant - but you need to provide it.