i have create a book but want to export it in read only PDF can i do this in LO writer
File > Export As > Export as PDF. In the dialog that opens, set your read only and other security attributes in the Security tab, make sure you choose a secure password (16 characters mix upper, lower, numbers but best to start with a letter).
Page 160 in the Writer Guide 6.4 from LibreOffice Documentation has more information. Cheers, Al