gci *.pdf | % {iex $("rar mf -m5 -rr1 {0}.rar '{1}'" -f $($_.BaseName -replace "\s+","."),$_.Name)}

Here is some explain:

• gci is Alias of Get-ChildItem
• iex is Alias of Invoke-Expression
• rar is the execution file which default locate at C:\Program Files\WinRAR