You could use the `basename` or `rename` command or a `for BLAH in "list"` loop would work..
for FILE in 'file1.pdf file2.pdf file3.pdf`
mv $FILE $FILE.scuba
This would rename file1.pdf to file1.pdf.scuba
And say if you have a bunch of files named the same but just have sequential numbers (file1 file2 file3 file4), you can make things easier on you by doing something like this:
for BLAH in `seq 1 10`
mv filename$BLAH newfilename$BLAH
Try searching this su bject matter, it's asked quite frequently and plenty of known good scripts out on the net, etc.