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Exhibit 10.18

VOTING AGREEMENT

        This Voting Agreement (the "Agreement") is made and entered into as of March 26, 2007, by and among TA/Advent VIII, L.P., Advent Atlantic and Pacific III L.P., TA Venture Investors L.P. and TA Executives Fund LLC (collectively, "TA Associates), JMI Equity Fund, III, L.P. ("JMI;" together with TA Associates, the "Equity Sponsors"), and Ronald and Mariette Woestemeyer (the "Woestemeyers"), all of whom are holders of Common Stock, par value $0.001 per share (the "Common Stock"), of PROS Holdings, Inc., a Delaware corporation (the "Company"). The Company, TA Associates, JMI, and the Woestemeyers are individually referred to herein as a "Party" and are collectively referred to herein as the "Parties." The Company's Board of Directors is referred to herein as the "Board."

RECITALS

        WHEREAS, the Equity Sponsors hold substantially all of the outstanding shares of the Company's redeemable preferred stock, par value $0.001 per share (the "Redeemable Stock") and hold a significant number of outstanding shares of the Company's Common Stock;

        WHEREAS, pursuant to the terms of the Company's certificate of incorporation, the holders of the Redeemable Stock are entitled to elect two (2) directors to the Board so long as the Redeemable Stock is outstanding;

        WHEREAS, the Company and the holders of the Redeemable Stock have agreed to the redemption of all the Redeemable Stock;

        WHEREAS, as a condition to the redemption of all of the Redeemable Stock, the Equity Sponsors desire the right, in their capacity as holders of Common Stock, to designate two (2) directors to the Board; and

        WHEREAS, the Woestemeyers hold or control 6,149,720 shares of Common Stock and desire to induce the holders of Redeemable Stock to agree to the redemption of Redeemable Stock by agreeing to vote their shares of capital stock in favor of the election of directors designated by the Equity Sponsors.

AGREEMENT

        NOW, THEREFORE, in consideration of the foregoing premises and certain other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties agree as follows:

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Signature page follows.

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        IN WITNESS WHEREOF, the Parties have executed this Agreement as of the date first above written.

      TA/ADVENT VIII L.P.

 
 
 
By:
TA Associates VIII LLC, its General Partner
      By: TA Associates, Inc., its Manager

 
 
 
By:
*

 
 
 
ADVENT ATLANTIC AND PACIFIC III L.P.

 
 
 
By:
TA Associates AAP III Partners, its General Partner
      By: TA Associates, Inc.

 
 
 
By:
*
*
Kurt R. Jaggers, Attorney-in-Fact		      
      TA VENTURE INVESTORS L.P.
Address:   
  
  
   By: *

 
 
 
TA EXECUTIVES FUND LLC

 
 
 
By:
TA Associates, Inc., its Manager

 
 
 
By:
*

Signature Page to Voting Agreement

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JMI EQUITY FUND III, L.P.

 
 
 
By:
JMI Associates III LLC, its General Partner

 
 
 
By:
  
      Name:   
      Title:   

 
 
 
Address:
  
  
  

 
 
 
  
Ronald Woestemeyer

 
 
 
Address:
  
  
  

 
 
 
  
Mariette Woestemeyer

 
 
 
Address:
  
  
  

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EXHIBIT A
ADOPTION AGREEMENT

        This Adoption Agreement ("Adoption Agreement") is executed by the undersigned (the "Transferee") pursuant to the terms of that certain Voting Agreement dated as of March 26, 2007 (the "Agreement") by and among the Company and certain of its stockholders. Capitalized terms used but not defined herein shall have the respective meanings ascribed to such terms in the Agreement. By the execution of this Adoption Agreement, the Transferee agrees as follows:

        EXECUTED AND DATED this            day of                        , 200    .

      TRANSFEREE:

 
 
 
By:
  
      Name:   
      Title:   
      Address:   
      Fax:   

Accepted and Agreed:
 
 
 

COMPANY
PROS HOLDINGS, INC.
 
 
 

By:
  
 
 
 
Name:   
      
Title:   
      

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EXHIBIT A ADOPTION AGREEMENT