I think that the file is not in the public domain. The editor is CD SHEET MUSIC and the pdf files of their CDs are copyrighted. (These pdf are not exact copies of old editions and constitute a new edition).
If it is a simple scan of an old manuscript, there is no problem but if you don't have the original manuscript to compare, you can't be sure unless CDSM write it. I think that CDSM is the 'editor' because I have their file and it is totally identical. Besides, before the total loading of your file, the logo CD Sheet Music appears on the top left of the page. --EDSO