The availability of Texas legal documents in PDF is somewhat limited. For more general help finding Texas law, see the law library's guides on Texas Legal Resources- Statutes and Texas Legal Research: Free Online Resources.
Texas legislative history materials are not available in PDF. For more help researching in this area, see the law library's Texas Legislative History Research Guide.
Thomson Reuters, that prints Vernon's Texas Statutes and Codes Annotated, lists the copyright date for each individual volume. For anything else, note that Tarlton has a collection of superseded volumes and pocket parts.