When selecting 'all' to download OM Web Viewer is downloading only first 10 reports which are viewable.
Output Management Web Viewer 12.1
To select "all" the reports, it is necessary go to each page and select all reports.
Increase the number of reports displayed on a page: This will need to be done by a SysAdmin:
This configuration change will affect all users. This uses a lot of resources and could slow everyone down if it needed to handle additional large numbers of report downloads. This setting may not be possible in your environment.