Navigate to the service plan and choose "Download songbook" from the Actions menu in the upper right.
A pop up will appear with some options for the resulting PDF file.
Here is a run down of the options:
Order of Service - includes a simple view of the order of service as the first page in the downloaded file
Song PDFs - includes all PDF attachments for any plan items which have songs linked to them.
Other PDFs - includes all other non-song related PDF attachments
Once you have finished making your selections, click on the "Download" button. This will download a single PDF containing all the files chosen below. This may take some time depending on how many attachments there are.