The retrieval of similar documents from the Web using documents as input instead of key-term queries is not currently supported by traditional Web search engines. One approach for solving the problem consists of fingerprint the document's content into a set of queries that are submitted to a list of Web search engines. Afterward, results are merged, their URLs are fetched and their content is compared with the given document using text comparison algorithms. However, the action of requesting results to multiple web servers could take a significant amount of time and effort. In this work, a similarity function between the given document and retrieved results is estimated. The function uses as variables features that come from information provided by search engine results records, like rankings, titles and snippets. Avoiding therefore, the bottleneck of requesting externalWeb Servers.We created a collection of around 10,000 search engine results by generating queries from 2,000 crawled Web documents. Then we fitted the similarity function using the cosine similarity between the input and results content as the target variable. The execution time between the exact and approximated solution was compared. Results obtained for our approximated solution showed a reduction of computational time of 86% at an acceptable level of precision with respect to the exact solution of the web document retrieval problem. © 2011 IEEE.