Permissions determine which users can access which functions of WorkLogPRO. Don't forget that JIRA's own settings and permissions may also affect functionality of the add-on. For example if you disable time tracking of JIRA, WorkLogPRO doesn't work.
Permissions specific to WorklogPRO can be accessed through the selected Project's own settings menu under Time tracking permissions at the bottom of the permissions list. You may refer to Managing Project Permissions page in Jira user manual to understand how permission management works.
There are two different permission sets for WorklogPRO, "Project Permissions" and "Global Permissions"
Project Permissions
View Own Worklogs: Gives permission to only view worklogs that are created by the users themselves. You also need "Browse Project" permission because without it you can't view the issue. To able to view worklogs of an issue, you need permission to view issue in the first place.
View All Worklogs: Gives permission to view worklogs that are registered by other users.
View Worklogs of Private Issues: You can mark some issues as "Private" using "Issues" configuration page of WorklogPRO. Worklogs of those issues are only visible to worklog author and worklog update author if work is registered by someone else in the name of worklog author. Using this permission you can give this permission to other users to. This is generally used to handle more personal worklogs like "sick leaves".
Work On Issues: Allow users to create worklogs on the issues.
Log Work for Others: Allows users to register worklogs for other users. You also need to "Edit All Worklogs" permission to create new worklogs for other users too. This is used to mark all worklogs created by a 3rd user as "Edited" worklog on the user interface.
Work on Uneditable Issues: Normally you can't log work for non-editable issues either using Jira's own 'log workLog Work' window or WorklogPRO's 'log workLog Work' window. This is determined by "jira.issue.editable=false" property of workflow status and usually this property exist for Resolved/Done/Closed status of issues and may exist on other workflow statuses as well. WorklogPRO allows you to override this behavior , you may specify project roles that may able log work for non-editable issues. You may specify multiple roles. If you don't specify any role for this setting no one will be allowed to 'log work' for non-editable issues.
Permissions specific to WorklogPRO can be accessed through the selected Project's own settings menu under Time tracking permissions at the bottom of the permissions list. You may access JIRA's permissions page through Managing Project Permissions page to understand in more detail.
Delete All Worklogs: You can give permission to delete all Worklogs that are entered to an issue. You can determine which users, groups, or roles will have this access. This is determined through JIRA's Permission Schemes.
Delete Own Worklogs: You can give permission to delete worklogs of the users own entered worklog information to an issueusing this permission.
Edit Own Worklogs: Allows users to edit their own worklogs.
Edit All Worklogs: You can edit all Worklogs that are entered to an issue. By all it means, not only you can edit the worklogs that you have entered yourself but all the worklogs that are entered by other users.
Edit Own Worklogs: You can only edit Worklogs that are entered by yourself to an issue. You can not edit any other Worklogs, meaning the Worklogs that are entered by other users, but only the Worklogs that are entered by yourself.
Work On Issues: This allows you to log work done against an issue. This is useful only if Time Tracking is turned on.
Approve Timesheets: There are two settings for timesheet approval. First you need to specify which project roles can approve worklogs for a project. Second you need to specify which user groups require their timesheet to be approved.
Log Work for Others: There is no separate setting for this. Users with 'Edit All Worklog' project permission can also log work for other users.
View All Worklogs: Gives permission to view worklogs that are entered by all users including Worklogs that are entered by the user himself/herself.
View Own Worklogs: Gives permission to only view worklogs that are entered by the user themselves.
View Worklogs of Private Issues: This allows you to only view worklogs that are made on private issues.
Work on Uneditable Issues: There are Issues that are uneditable by default. When this permission is given you may work on these issues as well.
Allow users to edit all worklogs even if worklog is created by another user.
Delete Own Worklogs: Allow users to delete their own worklogs.
Delete All Worklogs: Allow users to delete all worklogs even if worklog is created by another user.
Approve Timesheets: Allow users to approve timesheets for the project.
Global Permissions
Require Timesheet Approval: Allow users to submit their timesheet for approval. If a user is not covered with this permission schema, he/she doesn't need to submit their timesheet and related action will not be available on the Timesheet UI.
WorklogPRO Administrators: Allow users to modify most WorklogPRO global settings. Some features are still not available like scripts.