Edited to add unique permission setting info for a document:
- try go to the document -> View Properties -> "Shared With" -> click "Advanced" to get to the permission settings page
- click Stop Inheriting Permissions, there would be a popup saying "You are about to create unique permissions for this document. Changes made to the parent folder or document library permissions will no longer affect this document"
- config Anon access from there
original answer below
maybe this Q&A could help you?
(content taken from the link above)
Yes, you could do that. But first, you should enable anonymous at web application level, then site collection level for lists and libraries not entire web site. Then go to list permissions to enable anonymous access.
For more information, see http://blog.cloudshare.com/2012/10/15/how-to-enable-anonymous-access-to-a-sharepoint-2013-site/
You MUST have anonymous access enabled at the web application level, in order for you to activate it at the site level. The type of access you define in your site will define the actual access they will have.
Enabling anonymous access at the Web Application DOES NOT give users anonymous access to your site. It is however required in order to be able to select the 'Anonymous access' section if the permission management in your site.
If you specify 'Lists and Libraries' as the link above suggested, you can enable access to anonymous users to only those lists and libraries.
(more content taken from the 2nd link above)
As is the case in previous versions, you can configure SharePoint 2013 sites to be accessed by anonymous users. In this article I will show the steps needed to configure anonymous access to an existing SharePoint 2013 site.
Navigate to the SharePoint 2013 Central Administration in your SharePoint 2013 environment. Under Application Management section, click the “Manage web applications” link.
Select one of the available web applications and press the “Authentication providers” button available in the Ribbon. A modal dialog showing the authentication providers available per zone is displayed. As you can see, in a basic scenario only the “Default” zone is listed.
Click the “Default” link so a new modal dialog is displayed. Just check the “Enable anonymous access” option and press the “Save” button.
Navigate to one of the site collections you have created under the configured web application and go to “Configure -> Site Settings”. Under the “Users and permissions” section, click the “People and groups” link.
As you can see, SharePoint 2013’s Ribbon display is an “Anonymous Access” button that allows you to configure how anonymous users can access to the site.
Press the “Anonymous Access” button in the Ribbon so the related configuration modal dialog is shown. In this dialog you have three configuration options, just click the first one that provides full anonymous access to the site. Press the “OK” button.
Back to the “People and Groups” page, check there is a new group called “Anonymous users” available in the list.
We are almost done. To finish, start a new instance of a web browser and check that you don’t need to provide credentials information since anonymous access is enabled on the entire site.
And that’s all about how to enable anonymous access to a SharePoint 2013 site. I recommend you to check how it works in your SharePoint 2013 CloudShare environment.