Custom display forms do not display attachments in sharepoint designer 2010
Recently i came accross an issue that if you are creating a custom display form using Designer than it does not display the attachment controls thus it does not shows the attachments in that form.
After some google i came accross the solution that the attachment <tr> tag is not present in the custom form so u have to add it manullay
Below is the code just edit your display form and add this after the last <tr>
<tr><td width="190px" valign="top" class="ms-formlabel"><H3 class="ms-standardheader"><nobr>Attachments</nobr></H3></td><td width="400px" valign="top" class="ms-formbody"><SharePoint:AttachmentsField ControlMode="Display" FieldName="Attachments" runat="server" Visible="true"/></td></tr>You can also refer solution from Microsoft support site:Thanks!