PdfForge.Core 2.0.0

License file

PdfForge Licensing

📄 Commercial License

PdfForge is proprietary closed-source software distributed under a Commercial License.

Source Code Status

❌ Source code is NOT publicly available
❌ Source code is NOT open source
✅ Only compiled NuGet binaries are distributed
✅ You cannot view, modify, or decompile the source code

What You Can Do

✅ Use PdfForge.Core NuGet package in commercial and non-commercial projects
✅ Deploy PdfForge in production with a valid license
✅ Distribute applications that use PdfForge

What You Cannot Do

❌ Access or modify source code
❌ Reverse engineer or decompile binaries
❌ Redistribute NuGet package or binaries without a license
❌ Use beyond 30-day trial without purchasing a perpetual license

See LICENSE file for the full legal terms.

💰 Perpetual Licensing Model

PdfForge Core uses a 30-day free trial + perpetual licensing model for monetization:

Trial Period (30 Days)

Cost: Free
Duration: 30 days from first install
Features: All features enabled
Watermark: None
Activation: Automatic (no key needed)

Trial Expired (After 30 Days)

Status: Unlicensed
Features: All features still enabled (no feature gating)
Watermark: Red footer on every PDF ("PdfForge Trial Expired - Email rdaforge@gmail.com to license")
Action Required: Customer must purchase a perpetual license to remove watermark

Perpetual License (Lifetime)

Cost: One-time purchase
Duration: Forever (no expiry)
Features: All features enabled
Watermark: None
Activation: LicenseManager.Activate("PDFFORGE-[key]");

🔐 Trial Tracking

Trial start date is recorded in ~/.pdfforge/.pfstate with HMAC-SHA256 integrity protection to prevent tampering:

File Format: [datetime_ticks]|[hmac_signature]
Protection: HMAC-SHA256 computed from combination of constants
Behavior: Trial automatically expires on day 31 (no grace period)
Watermark Injection: Applied automatically when trial expires

🔑 Perpetual License Keys

Key Format

PDFFORGE-[BASE64URL_PAYLOAD]-[BASE64URL_SIGNATURE]

Payload Structure

{
  "p": "pdfforge.core",      // Product identifier
  "t": "perpetual",           // License type
  "iss": "2026-06-10"         // Issue date (ISO 8601)
}

Validation

Method: Offline HMAC-SHA256 verification (no internet required)
Key Derivation: SHA256 of "PdfForgeTrialIntegrityv1.0"
Security: Signature prevents unauthorized key generation

📊 License Status Enum

public enum LicenseStatus
{
    TrialActive = 0,    // 30-day trial in progress, no watermark
    TrialExpired = 1,   // Trial ended, watermark on PDFs
    Licensed = 2        // Perpetual license activated, no watermark
}

⚙️ API Usage

Activate License Directly

using PdfForge.Licensing;

LicenseManager.Activate("PDFFORGE-...");

// Generate PDFs without watermark
var pdf = new PdfBuilder().Build();

Activate via Configuration

var options = new PdfForgeOptions 
{ 
    LicenseKey = "PDFFORGE-..." 
};
options.Validate(); // Activates the key

// All subsequent PDF generation uses the license
var pdf = new PdfBuilder().Build();

Check License Status

var status = LicenseManager.GetStatus();
// Returns: TrialActive, TrialExpired, or Licensed

var daysRemaining = LicenseManager.TrialDaysRemaining();
// Returns: Days left in trial, or 0 if licensed/expired

var requiresWatermark = LicenseManager.RequiresWatermark();
// Returns: true if TrialExpired, false otherwise

var message = LicenseManager.GetStatusMessage();
// Human-readable status with purchase URL

🌍 Watermark Behavior

Status	Watermark	Text	Color	Pages Affected
Trial Active	❌ No	—	—	All
Trial Expired	✅ Yes	"PdfForge Trial Expired - Email rdaforge@gmail.com to license"	Red	Every page
Licensed	❌ No	—	—	All

📁 Implementation Files

Core licensing system (all in src/Licensing/):

File	Purpose
`LicenseStatus.cs`	Status enum
`LicenseManager.cs`	Public API entry point
`TrialTracker.cs`	Trial date tracking with HMAC protection
`PerpetualLicenseValidator.cs`	Offline key validation
`PdfForgeOptions.cs`	Configuration integration

Watermark injection (in src/Pdf/Writing/):

File	Purpose
`IWatermarkInjector.cs`	Watermark interface and implementations
`PdfWriter.cs`	Integrated watermark injection

🧪 Testing

Test Active Trial (No Watermark)

cd samples/HtmlBarcodeBatchSample
dotnet run -- --license-test

Test Expired Trial (With Watermark)

cd samples/HtmlBarcodeBatchSample
dotnet run -- --license-test-expired

The --license-test-expired flag backdates the trial to 31 days ago, simulating trial expiration and demonstrating automatic watermark injection.

💡 Customer Journey

Day 0:      Install NuGet package
            ✅ 30-day trial starts automatically
            ✅ Generate PDFs with no watermark
            ✅ All features enabled

Day 15:     Mid-trial
            ✅ Generate PDFs with no watermark
            
Day 30:     Last day of trial
            ✅ Generate PDFs with no watermark
            
Day 31:     Trial expired
            ⚠️ Generate PDFs WITH red watermark
            ⚠️ Watermark: "PdfForge Trial Expired - Email rdaforge@gmail.com to license"
            ⚠️ All features still work
            
Purchase:   Customer buys perpetual license
            > Receive license key: PDFFORGE-...
            > LicenseManager.Activate(licenseKey);
            ✅ Watermark removed
            ✅ License valid forever
            ✅ Can be distributed or renewed indefinitely

🛡️ Security

Offline Validation: License keys validated entirely offline (no internet/API calls)
HMAC-SHA256: Keys protected with industry-standard cryptographic signing
Tamper Detection: Trial start date protected with HMAC to prevent date manipulation
No Hard-Coding: Keys embedded in code are validated at runtime, not used for licensing decision
Open Source: MIT License - customers can audit the license validation logic

❓ FAQ

Can customers bypass the watermark?

Technically yes, since the code is open source under MIT License. However:

The license terms require removal of the watermark only with a valid license key
Removing watermarks without a valid license violates the PdfForge licensing agreement
Perpetual licenses are inexpensive (~$XX for lifetime access)

What happens if the `~/.pdfforge/.pfstate` file is deleted?

Trial tracking is restarted
A new 30-day trial period begins
This is a customer experience issue (discourages honest customers), not a security issue
Consider it part of the licensing contract: don't tamper with trial files

Technically yes (it's just a string)
Per the licensing agreement, each customer should have their own key
Future versions could add license activation tracking (phone-home model)

How are license keys generated?

Use PerpetualLicenseValidator.GenerateKey() (currently internal for testing):

// Example (internal API):
var key = PerpetualLicenseValidator.GenerateKey();
// Returns: PDFFORGE-eyJwIjoicGRmZm9yZ2UuY29yZSIsInQiOiJwZXJwZXR1YWwiLCJpc3MiOiIyMDI2LTA2LTEwIn0-[HMAC]

For production key generation, contact: rdaforge@gmail.com

📞 Support

For licensing questions or issues:

📧 Email: rdaforge@gmail.com

📅 Version History

Version	Date	Change
1.0.0	2026-06-10	Initial perpetual licensing implementation
2.0.0	2026-07-24	Licensing terms unchanged; released alongside the 2.0.0 security & correctness remediation

✅ Compliance

This licensing model complies with:

✅ MIT License terms (source code remains open)
✅ GPL compatibility (derivative works can be licensed under GPL)
✅ Commercial usage terms (no restrictions on commercial use)
✅ Distribution terms (licensees can redistribute under MIT)

The watermark is a business mechanism, not a license mechanism. It's applied at runtime on expired trials and does not modify the underlying MIT License of the source code.

PdfForge.Core 2.0.0 License Info