The pdftk can do a lot of what you are asking for, there is a free edition, ($0.00), and a pro-edition, (for a very reasonable $3.99), - both with windows GUIs and both include the cross platform command line server edition.
PDFTK Free GUI
PDFtk Server can:
- Merge PDF Documents or Collate PDF Page Scans
- Split PDF Pages into a New Document
- Rotate PDF Documents or Pages
- Decrypt Input as Necessary (Password Required)
- Encrypt Output as Desired
- Fill PDF Forms with X/FDF Data and/or Flatten Forms
- Generate FDF Data Stencils from PDF Forms
- Apply a Background Watermark or a Foreground Stamp
- Report PDF Metrics, Bookmarks and Metadata
- Add/Update PDF Bookmarks or Metadata
- Attach Files to PDF Pages or the PDF Document
- Unpack PDF Attachments
- Burst a PDF Document into Single Pages
- Uncompress and Re-Compress Page Streams
- Repair Corrupted PDF (Where Possible)
PDFtk Server does not require Adobe Acrobat or Reader, and it runs on Windows, Mac OS X and Linux.
The TOC could be produced by creating a separate PDF Document that contains the details and merging that in but AFAIK the consistent style would not be possible with this tool.
There is also the combination of Python, PDFMiner and ReportLab which could, with quite a bit more work setting things up, Merge, Generate TOC and reformat to a consistent style providing the original pdfs have been generated in a manner that allows this, i.e. not from a scanner and not from some programs that draw the text into the document in a complex manner.
Python and PDFMiner are free & Open Source.
ReportLab offers Free & Open Source (£0.00), paid for ReportLab PLUS, (pricing depending on pages/month generated and start at £1200 per annum doubled for the financial services industry), or bespoke solutions which unless their rates are really high may cost less to implement than roll your own if you include your development hours.