1. Convert PDF to JPG (The Web Way)
No installations – just browse to these websites, upload your files and it’s done.Zamzar

The minuses with the free service are that the file size is limited to 100MB with just 5 simultaneous conversions. Also, you might feel a wee bit uneasy uploading sensitive data without encryption support.
YouConvertIt (Beta)

As YouConvertIt is still in beta, expect some conversion attempt failures.
Neevia Document Converter

If you are wary of uploading sensitive files over the net, you need to look beyond the online solutions to something much more local. Thankfully these three pieces of free software take up the task.
2. PDF to JPG Converters for The Desktop
PDF-Xchange Viewer (Windows)
PDF-Xchange Viewer is a light feature-rich PDF document reader. The free version of the software is a capable document handler with most of the standard features expected. Add comments and annotations, mark-up pages with texts and objects, type within the PDF document along with plug-ins for both IE and Firefox are also included.But the feature which interests us is the ability of the software to export a file or a page to the supported image formats like JPEG, BMP, TIFF, PNG and more.

OmniFormat (Windows)

Using OmniFormat requires the installation of Pdf995 (it’s free too). Pdf995 is a fast and flexible PDF printer driver which makes it easy to publish PDF documents from any program. Pdf995 needs to be installed prior to the installation of OmniFormat. The free version of the software opens with a timed ad display.
This annoying part done with, the software itself is uncomplicated. It sets up a ‘Watch’ folder (or lets you set it up yourself). Any PDF file that has to be converted to JPG is copied into this folder. With the press of the ‘Single Pass’ button each single page of the PDF gets converted into the JPG format. With the ‘Start Monitoring’ button, PDF files can be repeatedly dropped into the watch folder for conversion.
Note of Caution: OmniFormat deletes the original PDF file in the watch folder after conversion…so be sure to copy the file you want to convert.
Virtual Image Printer Driver (Windows)

Simply, open the PDF file and print it by selecting the Image Printer Driver in the ‘Print’ dialog. The image file format and the compression range can be set in the Image Printer options box.