You need to specify atleast one input file, and exactly one output file
Use - for stdin or stdout

Usage: wkhtmltopdf [OPTION]... <input file> [more input files] <output file> 
converts htmlpages into a pdf

Options:
  -b, --book                      Set the options one would usualy set when printing
                                  a book.
      --cover <url>               Use html document as cover. It will be inserted before
                                  the toc with no headers and footers.
  -H, --default-header            Add a default header, with the name of the page to
                                  the left, and the page number to the right, this is
                                  short for: --header-left='[webpage]' --header-right='[page]/[toPage]'
                                  * --top 2cm --header-line.
  -n, --disable-javascript        Do not allow webpages to run javascript.
  -d, --dpi <dpi>                 Change the dpi explicitly.
      --enable-plugins            Enable installed plugins (such as flash.
      --encoding <encoding>       Set the default text encoding, for input.
      --footer-center <text>      Centered footer text.
      --footer-font-name <name>   Set footer font name (default Arial).
      --footer-font-size <size>   Set footer font size (default 11).
      --footer-left <text>        Left aligned footer text.
      --footer-line               Display line above the footer.
      --footer-right <text>       Right aligned footer text.
  -g, --grayscale                 PDF will be generated in grayscale.
      --header-center <text>      Centered header text.
      --header-font-name <name>   Set header font name (default Arial).
      --header-font-size <size>   Set header font size (default 11).
      --header-left <text>        Left aligned header text.
      --header-line               Display line below the header.
      --header-right <text>       Right aligned header text.
  -h, --help                      Display help.
  -l, --lowquality                Generates lower quality pdf/ps. Useful to shrink the
                                  result document space.
  -B, --margin-bottom <unitread>  Set the page bottom margin (default 10mm).
  -L, --margin-left <unitread>    Set the page left margin (default 10mm).
  -R, --margin-right <unitread>   Set the page right margin (default 10mm).
  -T, --margin-top <unitread>     Set the page top margin (default 10mm).
      --no-background             Do not print background.
  -O, --orientation <orientation> Set orientation to Landscape or Portrait.
      --outline                   Put an outline into the pdf.
      --outline-depth <level>     Set the depth of the outline (default 4).
      --page-offset <offset>      Set the starting page number (default 1).
  -s, --page-size <size>          Set pape size to: A4, Letter, ect..
      --password <password>       HTTP Authentication password.
      --print-media-type          Use print media-type instead of screen.
  -p, --proxy <proxy>             Use a proxy.
  -q, --quit                      Be less verbose.
      --redirect-delay <msec>     Wait some miliseconds for js-redirects (default 200).
  -t, --toc                       Insert a table of content in the beginning of the document.
      --toc-depth <level>         Set the depth of the toc (default 3).
      --toc-font-name <name>      Set the font used for the toc (default Arial).
      --toc-header-fs <size>      The font size of the toc header (default 15).
      --toc-header-text <text>    The header text of the toc (default Table Of Contents).
      --toc-l1-font-size <size>   Set the font size on level 1 of the toc (default 12).
      --toc-l1-indentation <num>  Set indentation on level 1 of the toc (default 0).
      --toc-l2-font-size <size>   Set the font size on level 2 of the toc (default 10).
      --toc-l2-indentation <num>  Set indentation on level 2 of the toc (default 20).
      --toc-l3-font-size <size>   Set the font size on level 3 of the toc (default 8).
      --toc-l3-indentation <num>  Set indentation on level 3 of the toc (default 40).
      --toc-no-dots               Do not use dots, in the toc.
      --user-style-sheet <url>    Specify a user style sheet, to load with every page.
      --username <username>       HTTP Authentication username.
  -V, --version                   Output version information an exit.

Proxy:
  By default proxy information will be read from the environment
  variables: proxy, all_proxy and http_proxy, proxy options can
  also by specified with the -p switch
  <type> := "http://" | "socks5://"
  <userinfo> := <username> (":" <password>)? "@"
  <proxy> := "None" | <type>? <userinfo>? <host> (":" <port>)?

Header and footer text:
In a header or footer text the following variables can be used
 * [page]       Replaced by the number of the pages currently beeing printed
 * [fromPage]   Replaced by the number of the first page to be printed
 * [toPage]     Replaced by the number of the last page to be printed
 * [webpage]    Replaced by the url of the page beeing printed
 * [section]    Replaced by the name of the current section
 * [subsection] Replaced by the name of the current subsection

Mail bug reports and suggestions to <antialze@gmail.com>.