Bar codes are part of SharePoint Information Management Policies (IMP) feature. If you need bar codes for your document, here are the steps to enable bar codes on SharePoint document library.
Steps to enable bar code in SharePoint:
In SharePoint 2013 (In SharePoint 2007 / SharePoint 2010 too!) enabling barcode is a simple two step process. (Lets use it with Document content type.)
Create new content type and enable bar code through Information Management Policies.
Add the content to required libraries.
Step 1: Create new content type:
Navigate to Site Settings >> Click on "Site Content Types"
Create New content type by clicking the link "Create"
Give a Name to the content type (E.g. "Project Plan"). Specify the parent content type as "Document Content Type" 
Enable bar code through Information Management Policies: From the content type settings page, Click on "Information Management Policies"
Click on "Enable Bar code" check box, and click "OK" to save changes.
Step 2: Add the content to required libraries
We've our content type with bar code enabled ready! Next step is to associate our content types to libraries wherever required.
Go to your target libraries where you need bar code functionality.
Navigate to library settings >> click on "Advanced Settings" >> Enable content types by clicking "Allow management of content types" to "Yes"
Now, from the library settings, Click on "Add from existing site content types" link under "Content Types" section.
Choose the content type we created at step 1 (In my case, it is: "Project Plan") and click "OK"
Modify the default view of the document libraries to include Bar code columns.
That's all! We are done! Create new document under the document library, See the bar codes in action!!
Same steps applies to SharePoint 2007/ SharePoint 2010 and for SharePoint 2013.
How to Set Custom value to SharePoint Bar Codes?
Well, But the problem is: SharePoint automatically generates unique 10 digit bar code value! we may not need it so in some cases, isn't it? we want to set bar codes to specific value.
Alright, How do I set bar code based on file's meta-data property? We can programmatically set Bar code values. Here is the sample code for SharePoint 2010 custom barcode generator.
You can place this code under event receiver to set custom barcode values. One draw back with the OOTB SharePoint barcode integration is: it supports only digits!
SharePoint 2010 custom bar code generator:
There are 3rd party components to these limitations and provides enhanced functionalities. Aspose Barcode is one among them. http://www.aspose.com/sharepoint/barcode-component.aspx
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