In HR, finance and legal workflows, PDF is the format most often used for sensitive content such as payslips, labor contracts, statements and reconciliations — and "distributing a batch of PDFs to different people" happens every month. Sending plain-text PDFs directly is risky: once a file is forwarded, anyone who receives it can open and read it. The traditional approach is to manually set an open password on each file with a dedicated tool before distribution; doing this for dozens or even hundreds of files is slow and easy to get wrong (some files simply get missed). On the receiving side, users often need a separate tool just to remove the password before they can read the file, which makes the whole loop inefficient.

The PDF AI capability of Spire.Agent.Office lets you describe what you need in natural language. The AI agent understands the request and completes the whole flow — "batch encryption → distribution list → decrypt on demand" — automatically.

Comparison with Traditional SDK API

This article shows how to use the Spire.Agent.Office PDF AI capability to set open passwords on a batch of PDFs and produce an encryption distribution list, then remove password protection on demand. Two cases demonstrate the two typical uses — encryption for distribution and decryption for archiving:

• Case 1: Batch-encrypt PDFs and generate a distribution list
• Case 2: Batch-decrypt password-protected PDFs

For product installation and SpireToken configuration, please refer to Integrating Spire.Agent.Office in a .NET Project. The examples below assume that Spire.Agent.Office has been installed and SpireToken has been configured.

Batch PDF Encryption, Distribution and Decryption

The core idea is: take one or more PDF documents to process as input, and let the AI agent set an open password on each one and save the encrypted copy — or remove the protection when the password is known — while keeping the original layout unchanged. The whole process of "file reading → password rule application → encryption/decryption → result output" is completed automatically by the AI, with no need to write per-file processing code. Case 1 below demonstrates batch encryption and distribution to recipients; Case 2 demonstrates how an administrator decrypts and archives the documents after they are collected back.

Case 1: Batch-encrypt PDFs and generate a distribution list

The most common batch-encryption scenario is adding an open password to many sensitive PDFs (such as employee payslips) before they are sent out. There are many files and each has a different recipient; if every file shares one password the protection is meaningless, but if passwords all differ they are hard to remember and communicate.

The example below uses the Spire.Agent.Office agent to treat every PDF in the attachments folder (i.e., all PDF files under the specified folder) as documents to be encrypted, assigns each one an independent open password based on the rule "employee date of birth + 4 random digits + @2026", saves the encrypted documents as PDFs, and at the same time produces an encryption distribution list that maps the original file name, the encrypted file name and the open password row by row:

using Spire.Agent.Office.AI;
using Spire.Agent.Office.Extensions;
using Spire.Pdf;

// Folder containing the PDFs to encrypt: every PDF in this folder is treated as an attachment (one per recipient)
string attachmentDir = @"E:\pdfs";  // folder that holds the PDFs to be encrypted
string[] attachmentPaths = Directory.GetFiles(attachmentDir, "*.pdf");

// PDF-related configuration
string inputPath = null;
string savePath = null;  // result path (null here: the output folder below will be used)
string OutDir = @"E:\output";  // output directory (encrypted PDFs and the distribution list are saved here)
string key = "**************************";  // SpireToken key
string instruction =
    "Read all the PDF files in the attachments and encrypt each one with an open password:" +
    "1. Generate the password for each file as 'employee date of birth + 4 random digits @2026' (for example, salary-1001.pdf corresponds to password 199805083371@2026). This open password only restricts opening the document and does not affect other functions such as printing, copying or editing;" +
    "2. Save every encrypted PDF to the output directory, appending '-encrypted' to the original file name, and keep the layout, fonts and page settings of the original document;" +
    "3. Generate an Excel-format encryption distribution list in the output directory, listing the original file name, encrypted file name and open password in each row.";

// Call the PDF document processing function
AIResult result = ExecuteDemoPDF(instruction, inputPath, savePath, key, OutDir, attachmentPaths);

// Execute PDF AI processing
static AIResult ExecuteDemoPDF(string instruction, string inputPath, string savePath, string key, string output, string[] attachmentPaths)
{
    // Create the AIOptions configuration object
    AIOptions options = new AIOptions();
    options.WorkDir = output;  // set the working directory to the output directory
    options.SpireToken = key;  // set the SpireToken key

    // Process the PDF document using a PdfDocument object
    using (PdfDocument pdf = new PdfDocument())
    {
        // Load the PDF document from file
        if (!string.IsNullOrEmpty(inputPath) && File.Exists(inputPath))
        {
            pdf.LoadFromFile(inputPath);
        }
        // Create the AI document processor
        AIDocumentProcessor processor = pdf.AI(options);

        // Execute the AI instruction
        return processor.ExecuteInstruction(pdf, instruction, savePath, attachmentPaths);
    }
}

The original PDF documents to be encrypted Batch-encrypted PDFs and the encryption distribution list

Every PDF gets an independent open password while the layout of the original document is preserved, and the encryption distribution list maps each file to its recipient's password so the sender can deliver it securely together with the files. When a new recipient is added later, you only need to put the new file into the attachments folder and rerun the instruction to complete the next round of encryption and distribution.

Case 2: Batch-decrypt password-protected PDFs

After recipients have finished reviewing, the administrator usually collects the files back for archiving and needs to remove the previously set open passwords in batch so the documents can be searched and merged. In this case the input file is empty; the encrypted PDFs and an Excel table that records the "file name / file password" mapping are provided together as attachments. The key to decryption is that the AI reads the open password of each file from the Excel table and opens the document with it.

The example below uses the Spire.Agent.Office agent with an empty input file. Through a natural-language instruction it reads the password-table Excel and the encrypted PDFs among the attachments, opens each document with the corresponding password from the table, removes the password protection, and saves the password-free documents one by one as PDFs:

using Spire.Agent.Office.AI;
using Spire.Agent.Office.Extensions;
using Spire.Pdf;

// The attachments are all the files under this folder (a password-table Excel plus the encrypted PDFs to decrypt)
string attachmentDir = @"E:\pdfs";  // folder that holds the password-table Excel and the encrypted PDFs
string[] attachmentPaths = Directory.GetFiles(attachmentDir);

// PDF-related configuration
string inputPath = "";  // empty input: all files to decrypt are among the attachments
string savePath = null;  // result path
string OutDir = @"E:\output-decrypted";  // output directory (decrypted documents are saved here)
string key = "**************************";  // SpireToken key
string instruction =
    "Read the 'file name / file password' mapping from the password-table Excel among the attachments and decrypt the matching encrypted PDFs in batch:" +
    "1. Read each row of the Excel to get its file name and the corresponding open password;" +
    "2. Locate the PDF document with the same file name among the attachments, open it with that row's password and remove the password protection;" +
    "3. Save each decrypted password-free PDF to the output directory, removing the '-encrypted' suffix from the file name, and keep the layout, fonts and page settings of the original document;" +
    "Save the final result as a PDF file";

// Call the PDF document processing function
AIResult result = ExecuteDemoPDF(instruction, inputPath, savePath, key, OutDir, attachmentPaths);

// Execute PDF AI processing
static AIResult ExecuteDemoPDF(string instruction, string inputPath, string savePath, string key, string output, string[] attachmentPaths)
{
    // Create the AIOptions configuration object
    AIOptions options = new AIOptions();
    options.WorkDir = output;  // set the working directory to the output directory
    options.SpireToken = key;  // set the SpireToken key

    // Process the PDF document using a PdfDocument object
    using (PdfDocument pdf = new PdfDocument())
    {
        // The input file is empty so nothing is loaded; all files to process come from the attachments (the password-table Excel + the encrypted PDFs)
        if (!string.IsNullOrEmpty(inputPath) && File.Exists(inputPath))
        {
            pdf.LoadFromFile(inputPath);
        }
        // Create the AI document processor
        AIDocumentProcessor processor = pdf.AI(options);

        // Execute the AI instruction
        return processor.ExecuteInstruction(pdf, instruction, savePath, attachmentPaths);
    }
}

The password-table Excel and the encrypted PDF documents to decrypt The decrypted password-free PDF documents

The "file name → file password" mapping in the password-table Excel is read and applied one row at a time, and the collected encrypted files are restored to password-free plain-text PDFs in batch, ready for archiving, searching or further merging.

FAQ

After setting an "open password", will printing / copying / editing be affected (besides needing the password to open)?

Cause: An open password and document permissions are two different things. The examples in this article only set an open password on the document and do not apply restrictions such as "no printing" or "no copying".

Solution: After encryption, apart from needing the password to open the document, the original functions such as printing, copying and editing remain unaffected. If you need to restrict printing or copying for security reasons, add a permission description to the instruction (for example, "view only; printing and copying are not allowed") and the AI will configure the corresponding permissions accordingly.

Does encrypting a PDF with an open password change its layout?

Cause: Encryption only affects opening and permission validation of the document; it does not reflow the page content.

Solution: Spire.Agent.Office preserves the layout, fonts and page settings of the original documents during encryption. If you are concerned about a particular style change, add "keep the layout, fonts and page settings of the original document" to the instruction.

Getting a SpireToken Key

• Contact sales@e-iceblue.com or visit https://www.e-iceblue.com/TemLicense.html to obtain a trial/commercial API key

Configure it in your code:

AIOptions options = new AIOptions();
options.SpireToken = key;