You can attach a document to four types of entities:
a contract
a building
a unit
a person (tenant, owner, guarantor, service provider)
The entity you choose determines where the document is filed. To understand which document goes where, see How do I organise my documents?
Steps
Open the relevant entity:
Contract: Contracts menu, then click the contract.
Building or unit: Properties menu, then click the building (and, if needed, the unit inside it).
Person: Address book menu, then click the contact.
On the entity's page, click the Documents tab.
Click Add a document.
Add the file: drag it into the drop area, or click Select a file (maximum size: 20 MB).
Choose a Category. If none fits, choose Other.
If you wish, give the document a Title (optional) and adjust the Date.
Click Add.
The document is then saved on the entity and accessible from its Documents tab.
