Attach Files to Inventory Record

Navigate to Customization > Lists , records & Fields > Item Fields 
Label = Inventory File Attachment
Store Value = Checked 
Type = Document 

On the Applies to Tab 
Inventory = Checked

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On the Item Record you will see the below:

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Once you add a document it will show the file name while on 'EDIT' mode

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In Viewing mode the field will show a download link for the file.

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