Merge PDF files online(with simultaneous rotating, resizing and numbering) – fast and secure. Go to the encrypted site: https://www.konwerter.net/en/mergepdf/
More advanced version( multiple files choice, rotation, resizing and numbering of combined files simultaneously) https://www.konwerter.net/en/mergepdf2/
Alternatively, you can perform PDF combining via e-mail – simply add attachments and send a message. Further instructions below.
1. Address a message to firstname.lastname@example.org or click in the link: Merge PDF
2. Add as many attachments as you like
3. Send your message
Name you files in preferred order. Example: 1.pdf 2.pdf 3.pdf or file1.pdf file2.pdf file3.pdf
If you need more security, use PGP encryption http://www.konwerter.net/pgp-encryption/