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Both deals are subject to regulatory approval, but are expected to close by the end of June.
Symantec said the companies' combined specialties in standards-based encryption for e-mail, file systems, removable media and smartphones will complement its security offerings.
Analysts said the acquisitions will open the way for Symantec to fill the gaps of full-disc encryption for desktops and laptops in its products.
The fast-growing encryption market is estimated to reach $1.7bn in 2013, according to IDC.
"With these acquisitions we can further protect information by using encryption in an intelligent and policy-driven way to give the right users access to the right information, enabling the trust that individuals and organisations need to operate confidently in an information-driven world," said Francis deSouza, senior vice-president, Enterprise Security Group, Symantec.
He claimed Symantec is now able to offer the industry's most comprehensive solution across encryption and data loss prevention for protecting confidential data on endpoints, networks, storage systems and in the cloud.
The deal follows similar acquisitions by McAfee and Sophos aimed at adding encryption technology to their products.
McAfee paid $350m for Safeboot in 2007 and Sophos paid $288m for Utimaco in 2008.
Symantec plans to standardise its products on PGP's key management platform, which allows administrators to manage encryption tasks centrally.
That platform will be integrated into the Symantec Protection Center management console.
GuardianEdge, which specialises in security for laptops, portable storage devices and smartphones, is already a partner of Symantec for its Endpoint Encryption product.
The two companies will become part of Symantec's Enterprise Security Group, headed by DeSouza.
"It's terrific that enterprises are looking to encryption as a first line of defense against criminal attack," said Wasim Ahmad, vice-president at Voltage Security.
"This acquisition gives Symantec an email and laptop encryption solution for protecting endpoint data. It underscores the importance of encryption within an organisation,” he said.
But businesses should take a data-centric security view of sensitive data and take additional steps to ensure data is protected wherever it goes, said Ahmad.