1. Open up the .aspx file responsible for displaying the document list in Sharepoint Designer, in my case it is called AllItems.aspx

2. Select the WebPartPages:ListViewWebPart control. (It is the place where rows of document are listed)

3. Right-click on it, Convert to XSLT Data View

4. Go into the code and find the line that says:

<xsl:value-of select="ddwrt:UrlBaseName(string(@LinkFilename))" />

5. Add this to the end of the line:

.<xsl:value-of select="@File_x0020_Type" />

6. Save

Caution: after editing the file with sharepoint designer, you wouldn’t be able to edit it with anything else except maybe Visual Studio