By Philipp Gollner

SAN FRANCISCO (Reuters) - Hewlett-Packard Co said on Monday it is launching a $300 million marketing campaign to promote Web-based printing services as it seeks new uses for printers, the company's most-profitable business.

The campaign, involving traditional media, outdoor ads and online content, begins on Tuesday and promotes HP's "Print 2.0" effort announced in May. This aims to more closely tie printing to the Web as printer use changes quickly in the digital age.

"As more and more content moves from the desktop to the Web, HP is working to make printing relevant and meaningful," the company said in a statement.

HP hired Omnicom Group Inc's Goodby, Silverstein & Partners of San Francisco, which has done HP ads since 1996, for a campaign to reach all countries where HP is present.

HP earns about 28 percent of revenue and more than half its operating profit from its imaging and printing business, run by Vyomesh Joshi. Ink cartridges generate most of those profits.

HP is targeting consumers, small businesses and graphic artists with a campaign that is "not about the printer" but about what they can do with it, Joshi said in an interview.

For example, HP technology could help blend online photos and text into a book of pictures from the current concert tour of singer and fashion designer Gwen Stefani, and then print the album at home, work or at a print-service provider.

Small and medium-sized businesses can turn to an HP Web site to create business cards and letterhead based on templates designed by graphic designer Paula Scher, HP said.

HP has agreed with Microsoft Corp to let users of the Windows Live Spaces social-networking service print their own or friends' online photos using technology from Snapfish, an online digital-photography company HP bought in 2005.

HP, based in Palo Alto, California, also announced a partnership with Yahoo Inc to provide a Web browser toolbar giving users access to printing tips, creative projects, customer support and online classes.
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