User wg9s offers several current SeaMonkey builds from latest source for WINDOWS, MAC and Linux.
SeaMonkey 2.53.2 is the new successor of 2.53.1, German version works fine for me on WIN, English Version and other OS not (yet) Tested by me.
Reports on Expereience are welcome, but please be aware that you use those builds on your own risk. I recommend to create a backup of your user profile before you start testing those builds.
PDF Viewer for SeaMonkey 2.1.288 does not work correctly with SeaMonkey 2.53 and 2.53.1 (By WG9S): endless idling in Browser-TAB until you click Stop Loading Icon, also problems when open PDF attachment from Mail.
There is a first experimental fixed version (by FRG) here, you can use it for tests on your own risk. Loading PDFs in browser window now works fine, loading PDF attachment from email still needs a refresh (browser tab contents) before PDF becomes shown.
More details and discussion on German Blog.
SeaMonkey Internet Suite 