This one works for Acrobat Pro (tried in Acrobat X and XI)
1. Click on Tools button on the right and choose 'Document Processing' (If not present, you might need to activate the 'Document Processing' tab by clicking on View Menu > Tools > Document Processing)
2. Click on 'Remove all links' option.
3. The warning tells you that this is non-reversible. Accept and it will tell you how many links were removed.