If you want to reserve document numbers at the start of a project, create placeholder documents.
Placeholders act as ‘envelopes' within Aconex. You can create a placeholder at any time.
If you are creating one or two placeholder documents follow this article - Create a placeholder.
If you are creating more than a few placeholder documents follow this article - Create multiple document placeholders at the same time.
You can supersede placeholders with the required document at any time during your project. Follow the steps here - Supersede a single document
Placeholder documents are usually used:
Ask your Org Administrator to check the Project Settings for your project.
If you are an Org Admin or a Project Administrator