You would need to use the Find and Replace feature to do this.

One thing to remember is that you will need to use spaces in you find string!
I.E.:

Find
1.1
Replace
1.5

will also effect 1.1.1 or 2.1.1, etc

so, instead try:

Find
1.1(SPACE)
Replace
1.5(SPACE)

to prevent this!

Open a copy of the document and have a play to see how it works!