# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/https?:\/\/\S+\/([^\s\/]+\.pdf)$/replacement $1/gm;t' <<< "http://www.oldsite.com.au/*.pdf
https://www.newsite.com/wp-content/uploads/2021/01/*.pdf
http://www.test.com/a.b.c.pdf"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html