In your InDesign document, choose File -> File Info ... and fill in the fields with useful default data. The "Title" and "Author" fields will appear as such in any PDF that gets exported from it, as can be seen in "Document Info" in Acrobat Reader or Pro. The "Title" will also appear if you select to show the title, instead of the default file name, in the title bar on opening the document.
And they appear in Google if the PDF is put online, so it might be a bad idea to plainly state "Do Not Distribute" into these fields. But all of the other fields of File Info also get stored in any PDF, so you can fill in a default "Description Writer" , "Copyright Notice", and "Copyright status".
Apart from that: it's even possible to add custom data with the File Info field, and that will also get stored into any exported PDF.
Note that any and all information in the File Info field only gets exported by InDesign on a straightforward export to PDF. Printing to a file, then distilling it, for example, will not retain it.
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