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On downloading PDF files from Internet in the form of e-books, documents, white papers, manuals, etc, it is commonly found that the contents cannot be copied or edited. This is because most PDF files are secured either with encryption passwords or with local restrictions. Usually authors of PDF documents impose local restrictions on the files after creating them so that users cannot modify the data. This helps especially while transferring the PDF files over the Internet against tampering or unauthorized access. Such restrictions make it impossible to edit or copy data from PDF files, extract pages, fill forms, modify images or tables, assemble the documents, create template pages or even sign the documents. However, sometimes it becomes necessary to unprotect PDF files for accessing data in all ways mentioned before. A few times it also happens that the authors themselves lose the PDF passwords after imposing the restrictions and are unable to open the documents for making changes. For all this reasons, it becomes essential to unprotect PDF documents by lifting the local restrictions. Software utilities developed for removing restrictions are used for this very purpose. Kernel for PDF Restriction Removal Tool is one such utility that enables users and document authors to remove the imposed restrictions and unprotect PDF files. With the help of PDF restriction removal tool, all types of local restrictions can be eliminated as these support 40 bit RC4 and 128 bit RC4 decryption algorithm, with which they unprotect PDF files. To unprotect PDF documents, such tool open the secured files, extract data from them and save them in newly created PDF files. New PDF files are created with all the restrictions removed and data integrity preserved. The secured documents are considered as read-only copies and are thus kept unchanged. Using such tools, large sized PDF files can be accessed easily, no matter what version of Adobe Acrobat is used for their creation.
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