Softwares like Turnitin and IThenticate serve the purpose for the plagiarism check of the documents, but they have their own databases to check from and compare with the provided document.
According to the https://uwaterloo.ca/academic-integrity/integrity-instructors-and-tas/turnitin-and-ithenticate,
Turnitin can be used as both a plagiarism tool and an educational tool. Turnitin generates ‘similarity reports’ on student submissions which can provide instructors with information about plagiarized sources. The reports can also be used as part of a formative or low-stakes assessment to help students understand the proper use of quotation marks, how to cite sources properly, and how to paraphrase.
iThenticate is plagiarism detection software that is designed to be used by researchers to ensure the originality of written work before publication. For example, graduate students and researchers can check their articles and book chapters to be submitted for publication, grant proposals, theses and dissertations.
These softwares are usually not available to the working professionals outside academia.
Are there any good softwares which can be used to check plagiarism in LORs and SOPs?