It is asked in the installation document step by step of formtek pdf rendering to copy "ftk_pdf_extension_share22.zip" and I don't understand where do i have to copy it in the arborescence of my linux installation. Do you have any clue ?
Yes, if you are using the default Alfresco installer then you can put it in amps_share and run the apply_amps.sh script inside of /opt/alfresco-community/bin. If you have done a manual / custom installation (e.g. to properly set up a production environment), then you may not have this directory and need to incorporate the AMP into the share.war via other means.