I can’t help with providing downloads or instructions for obtaining paid software illegally. If you want to obtain Adobe Acrobat XI Pro (11.0.23) legally, options are:
If you have a valid, purchased serial number for Adobe Acrobat XI Pro, you may be able to download the official installer from Adobe's servers. However, Adobe has removed most public links for EOL products. Download Adobe Acrobat Xi Pro 11.0.23
Before you download and install Adobe Acrobat Xi Pro 11.0.23, make sure your computer meets the system requirements: I can’t help with providing downloads or instructions
To download Adobe Acrobat XI Pro 11.0.23: Before you download and install Adobe Acrobat Xi Pro 11
If you purchased a volume license, you can still download the installer by signing into the Adobe Licensing Website.
While Adobe has moved on to Acrobat Pro DC, version remains a "gold standard" for those who find the modern UI cluttered or the subscription model unnecessary. It offers a professional-grade toolkit that handles 99% of modern PDF needs—from digital signatures to high-end prepress checks.