TracAttachmentNumMacro is a Trac macro that allows to link to attachment of the current wiki or ticket by number, which is useful for generic pages etc.
Put the following code into your Trac configuration file trac.ini:
tracattachmentnum.* = enabled
# Optional default settings
raw = True
format = short
# ATM format is only 'short' or 'long' (default)
[[AttachmentNum(1)]] # First attachment, result: "attachment:'first.doc'".
[[AttachmentNum(1,raw=True)]] # First attachment (raw link), result: "raw-attachment:'first.doc'".
[[AttachmentNum(1,format=short)]] # First attachment, hyper-linked filename is printed only, result: "first.doc".