I am using LibreOffice Version: 220.127.116.11, Build ID: 430m0(Build:2). There seems to be a bug in Export to pdf. Ordinary hyphens, i.e. - (hex 2d) get erroneously converted to hex ad, on export to pdf. They LOOK all right in the pdf document, but if you select text including such a hyphen in the pdf document, and copy it to clipboard, you get hex ad instead of hex 2d. This shows up if you try to copy and paste a url containing hyphens, properly hex 2d, into a browser address bar. I have also checked using a hex editor, specifically KHexEdit, that the dashes which should be hex 2d are hex ad. I have also done the copy and paste from pdf operation in 2 different pdf viewers, namely KDE Okular, and also in the Evince document viewer, which is a Gnome type of document viewer. I have URL Recognition UNCHECKED in Tools | AutoCorrect Options, but this is not actually relevant, since the problem occurs for hex 2d hyphens that are not in URLs, too. I have tried unchecking Replace dashes in Tools | AutoCorrect options, but that does not seem to help either. I am using Debian GNU/Linux, Jessie, and the Trinity Desktop Environment, but I doubt this is relevant to the problem.
In response to the comment by ajlittoz below, I did actually check that if I copy and paste directly from LibreOffice, I do correctly get hex 2d for hyphens, that is both for hyphens that I type in myself, and for hyphens when I paste in a url from the clipboard. I checked that by copying and pasting from LibreOffice into KHexEdit. I have done that again just now for the url of this page, which contains lots of hex 2d hyphens. So the hex 2d hyphens are correctly hex 2d in the text in LibreOffice, the erroneous conversion to hex ad occurs when I do Export to pdf. Thank you ajlittoz for the quick reply.