You may take advantage of the PDF templates provided by the Latvia Localization SuiteApp. These templates include the mandatory information.
[STA] Latvia Invoice PDF/HTML Template
[STA] Latvia Invoice with VAT Summary PDF/HTML Template
[STA] Latvia Sales Goods Invoice PDF/HTML Template
[STA] Latvia Credit Memo PDF/HTML Template
...
[STA] Latvia Credit Memo with VAT Summary PDF/HTML Template
These can be used as a template or can be assigned to an existing transaction form.
...
Go to Customization > Forms > Transaction Forms
Click Edit next to the transaction form.
On the PDF Layout drop-down field, select the template.
Click the Save As button.
...
For questions or concerns, please contact support@staria.com.