Document upload in sharepoint 2010

Question

When we upload any office document in sharepoint document library do sharepoint make any changes or add properties to the document?

Answer 1

It depends upon the SharePoint application and also the Office version (e.g., use of Document Parsing & Record Center Sites - where doc properties are related to the site content) - see this post for an example & more details: The Case of the Missing Office Document Properties in SharePoint 2010.

Answer 2

As far as I know SharePoint is not making any changes when you upload the document it just extracts the properties matching columns in the library, but when you access the document from a document library SharePoint will add/update these properties in the document.

But the result is the same.
Your document will not be unchanged when you retrieve it later.