PDF-XChange Viewer, pdflatex, Windows XP Pro SP3
Solution 1:
PDF-XChange View supports a command line option
pdfxcview /A "nolock=yes=OpenParameters" document.pdf
which opens a PDF file called document.pdf lock - free. In this case PDF-XChange View asks on change if the document should be reloaded. You can then enable automatic reloading on change. Useful when working on PDF files and frequently checking created output.