Does anyone have Adobe Acrobat Pro 11's serial no?

Why don't you try using the Adobe free trial for a bit to see whether the software you want to download for free is any good or not anyway?
I think most Adobe stuff have a free download and 30 days trial, then you have to pick whether it's worth paying for or not.

Also, of all the Adobe software, Acrobat is probably one of the easiest to find a free replacement to.
There are so many Opensource and freebie PDF editors and readers out there now, that there's really no need to go down the pirated software route.

For example, here's a list of some to check out, courtesy of Cogniview.com -

1. CutePDF:
   Create a PDF file from almost any printable document. CutePDF has an
   open SDK and doesn’t bog down their software with popups or watermarks.
2. Adobe Online PDF Creator: The online version of the popular Adobe Acrobat.
3. PDF reDirect:
   The freeware PDF reDirect offers loads of robust features, including
   PDF creation, previews, encryption, and more, that go a long way to
   replacing Adobe.
4. CC (Free) PDF Converter: This printer driver can be used to create a PDF file from any printable Windows application.
5. PDFCreator: Use PDFCreator to create PDFs from any printable program, as well as encrypt and autosave files based on predefined terms.
6. Open Office: Open Office has a PDF export feature that allows you to define compression levels as well as handle thumbnails and hyperlinks.
7. Scribus: Use this desktop publishing program to create interactive PDF presentations and forms.
8. HylaFAX: HylaFAX is an open source fax server that can be configured to deliver in PDF.