When you change a reservation, you have to recreate documents and click Create again in order to apply the changes:

1. Edit a reservation.
2. Find the Documents field and click Create next to the document you wish to recreate.
3. The Creating document window will appear.
4. Fill in the parameters.
5. Click Create to recreate the document.

NOTE: Newly created documents will keep the same number.
IMPORTANT: If you create a document in one year, it is no more possible to change its date to another year. This is forbidden because otherwise it will create a break in document numbering.