In the online environment, free guitar scores generally can be found and downloaded in either of two ways:

(A) One can search the online catalogs of libraries that have special collections of mostly older, public domain guitar music that has been digitized as a public service. GFA member Robert Coldwell has developed a cross-platform search engine for the 14,000+ public domain scores that are now searchable online. It also allows you to search the specific collections that offer digitized scores. The world-class collections that freely provide digitized guitar scores (facsimiles, usually PDFs) online include the following at this time; links are provided to each collection for those who wish to search them directly:

Boije, 1661 scores

GFA Archive, 270 scores

Hudleston Collection of guitar music, over 1,000 scores of solo and chamber music

Lester S. Levy Collection of Sheet Music, guitar items only, 384 scores

Library of Congress - Music for the Nation, guitar items only, 1187 scores

Library of Congress - Edison Sheet Music Collection, guitar items only, 51 scores

Rischel & Birket-Smith, 1553 scores

Remember that the foregoing are a subset of a larger universe of some 13,000+ cataloged guitar scores, the majority of which are not yet digitized. At least their cataloging information is available online! The latter, held in collections around the globe, are searchable at Mr Coldwell's Digital Guitar Archive search site. 

(B) One can search peer-to-peer sites, and take one's chances. The results can sometimes be both huge and surprising. Some links to peer-to-peer sites are provided at the bottom of our Guitar Music Scores page - a part of the GFA's Guide to Research Resources Online.  If one wishes to search an institutional version of the many peer-to-peer sites, perhaps the best would be:

IMSLP.org, which stands for International Music Score Library Project is the largest site specifically for known or suspected public domain (PD) music scores in the world. Hosted in Canada, it attempts to enable "sharing” of these scores as much as possible while still striking a reasonable balance between three divergent copyright protocols: Canada (where it is hosted, and where any score or recording whose creators died before 1963 is considered public domain), the United States (where 1923 is currently the date before which the work must have been published in order to consider it Public Domain today), and the European Union (where the works of any creator who died before 1943 [or 70 years ago] are now in the Public Domain).

Works for guitar solo include method books (like the Gaspar Sanz Instrucción de Música sobre la Guitarra Española of 1674) and scores: historical facsimiles (often lifted from the digitized scores provided by the libraries listed above) and a few contributed modern typeset editions of questionable accuracy and uncertain ”public domain” status.

When a score is available to download, the reader must first acknowledge the IMSLP disclaimer, which stated (in June 2013):

The site has thousands of pages of guitar music, solos all the way to guitar ensembles, so should be routinely searched by any guitarists who understands the issues and conditions to which IMSLP.org is seeking to respond. Its database design, enabling searching with a broad range of limiters and refinements, is excellent.