help
If you have a SW drawing file open do a "Save As" and pick PDF file extension and the a dialog box should pop up, then pick the drawings you want save as PDF.. I do this with every project..
You can't natively (is that a word?) save multiple drawings as 1 PDF file.
However, as Markku Lehtola has pointed out, there are utilities that will enable you to combine PDF files once you have saved out all of your individual drawings as separate PDF files.
There are other options as well.
Inside #TASK (TASK), it has a utility to merge drawings, which you could then save out as a single PDF file.
As mentioned above if you get Adobe Standard you can combine PDF's with little effort.
PDF Task – Combining files