If you need to protect PDF with a password, you can use Adobe’s own tool or a third-party application. In this article, we will analyze the ways how to encrypt multiple pdf files.
Basic principles of encryption of the PDF multiply files
Portable Documents Format (PDF), developed by Adobe Systems, Inc., is designed to store documents that are presented in electronic form. PDF is the main format of the Acrobat family of products. Adobe reader facilitates the opening, viewing, and printing of PDF documents. The browser automatically detects the adobe reader during installation and installs a plugin for it. After that, you will be able to view all documents in the specified format.
You, as users, will be able to add comments, graphic notes, callouts, lines, and more. Unfortunately, in practice, there is no program that can completely protect a document from copying.
One of the elements of comprehensive information security measures for multiplying PDF files is cryptographic information security. This type of information protection is implemented by transforming information using keys based on mathematical methods.
Encryption allows you to protect information by converting it into incomprehensible text (ciphertext) with the possibility of further decryption. You can encrypt both plain text and computer files. Encryption is divided into symmetric and asymmetric. Symmetric encryption uses one secret key for both encryption and decryption. Asymmetric encryption uses a public key for encryption and another, a secret key for decryption, which is generated by pseudo-random number generators.
Besides, you can also transfer your PDF files into virtual data room software, that also uses encryption of critical-business documents.
What about Adobe security?
Encryption support was added in the second version of the specification (PDF 1.1), but the initial version of the security algorithm was not very successful – it seems that the same key was used repeatedly when encrypting with the RC4 streaming algorithm. For more flexible control of the encryption key calculation procedure, Acrobat family products support so-called security handlers, which can be plugged in through plug-ins. Initially, Security Handler was only responsible for calculating the encryption key of the document, and all encryption operations were performed by Acrobat itself. Prior to Acrobat 5.0, the official document encryption key was always 40 bits long due to export restrictions. However, Acrobat Reader 4.0.5 already supports longer keys used to protect ebooks. Starting with Acrobat 5.0 (and the corresponding PDF 1.4 specification), two new versions of the security algorithm have been added, allowing you to work with keys up to 128 bits long. In Acrobat 6.0 (PDF 1.5 specification), the security module has the ability to not only calculate the encryption key but also perform the encryption itself.
The most common way to set up a password for multiply PDF files is to use Adobe’s own Adobe Acrobat Pro tool. Here’s the guide on how to do it:
Download files. You can be sure that your files will be securely downloaded over an encrypted connection. They will be permanently removed after processing.
- To upload files, click the “Upload PDF File” button and select the files you want to edit or drag and drop them onto the page.
- To upload files from Dropbox, Google Drive, or the website where files are located, expand “Upload PDF File” and select your files.
Create a strong password. Create your strong password and enter it into the form. It is recommended to use a 16-character password in combination with numbers and symbols. Each time a user opens a PDF document, a password will be required to access and open it.