If you encrypt it how would anyone read your blog? You would need to give them the key and then the encryption goes away - Adobe Acrobat has some security features that I think make it harder to copy and or print a document (I lock viewers from changing the file on many of my downloads - if they are going to steal content then they will need to work a bit) - but if you made a whole blog of PDF files I doubt you would have many visitors.
Bottom line - your content will probably be lifter in some manor if it is valuable or appealing - I have several sites that take my RSS feed for boating safety and display the summery of my last article or ID my site as a site for boating safety - they want people to go to their site for say boating insurance and having a lot of links to sites with boating info is one way they try and get traffic to their site.
There have been some cases that came through the Forum where entire blogs were inserted into "Scrapper" sites - that can be dealt with but a bit of a hassle -