pdftk takes the input files first.

Joining pdfs:

pdftk file1.pdf file2.pdf cat output output.pdf

Bursting pdfs into pages:

pdftk file1.pdf burst

Extracting particular page ranges. Following example removes pages 10-25:

pdftk file1.pdf cat 1-9 26-end output holy.pdf

And of course, extracting a particular page:

pdftk file1.pdf cat 10 output p10.pdf

Man lists the following options:

<operation> may be empty, or:
    [cat | attach_files | unpack_files | burst |
    fill_form | background | stamp | generate_fdf
    dump_data | dump_data_fields | update_info]

These are explained by the mother page as:

• Merge PDF Documents
• Split PDF Pages into a New Document
• Decrypt Input as Necessary (Password Required)
• Encrypt Output as Desired
• Fill PDF Forms with FDF Data and/or Flatten Forms
• Apply a Background Watermark
• Report on PDF Metrics such as Metadata, Bookmarks, and Page Labels
• Update PDF 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)