If you use the "Require password to open the file" option, the pdf will be encrypted according to the help files:

If either password option is specified in the PDF file, the file will be protected and its contents will also be encrypted. An encrypted PDF file's content appears as "unreadable text" when opened using non-PDF reading applications. The file's content cannot be indexed by the operating system and search engines, which means users will not be able to search for content within the document using desktop and internet search utilities.

http://www.filemaker.com/11help/html/non_toc.45.39.html

But is it 40 or 128-bit?

Here's a $99 product that guarantees that it can crack a 40-bit key (even if it takes several days) and a $399 product that will do it in minutes, but it doesn't guarantee it can do this for 128-bit.

http://www.elcomsoft.com/apdfpr.html

If you open the file in Adobe Reader and examine its properties, it says "Encryption Level: 128-bit RC4".