In my Ubuntu Server 12.04, I am converting all .docx files under a directory to .pdf files with this command:

libreoffice -headless -convert-to pdf:writer_pdf_Export *.docx

Can I merge multiple documents and convert them to single .pdf file like this?

For example:

file1.docx

file2.docx

file3.docx  

And the output should be one .pdf file like merged_result.pdf. I have to do it from Terminal because I'm using it in PHP.

Furthermore, can I add picture like front image? Any kind of source I can get the Terminal functions for LibreOffice is appreciated, too; I was unable to find what I'm looking for.

Thanks in advance.