PDFlib PLOP

PDFlib PLOP (PDF Linearization, Optimization, Protection) is a versatile tool for linearizing, optimizing, repairing, analyzing, encrypting and decrypting PDF documents.

The extended version PLOP DS (Digital Signature) supports all features of PLOP plus the ability to apply digital signatures to PDF documents.

• PLOP linearization and optimization features create efficient and small PDF documents for fast Web delivery.
• PLOP protection features encrypt or decrypt PDF documents and apply or remove permission settings, such as »printing not allowed« or »content extraction not allowed«.
• PLOP’s repair mode automatically detects damaged PDF documents and fixes the problems if possible.
• PLOP analysis features can be used to query arbitrary properties of a PDF document.
• Document info entries and XMP metadata can be retrieved and set in a PDF/A- and PDF/X-conforming manner.

With PDFlib PLOP you can linearize a PDF document for fast delivery over the Web (byteserving). Byteserving increases the perceived download speed since the first page is already visible while the remainder of the document is downloaded in the background.

PLOP can significantly reduce the file size of a PDF document without affecting quality. It achieves this by removing unnecessary or redundant identical objects, such as repeatedly embedded fonts, images, identical ICC color profiles, etc.

PLOP can apply user and master passwords, and set permission restrictions to prevent the document from being printed with Acrobat, disallow text extraction or modification, etc.

PLOP supports strong AES-256 encryption and Unicode passwords. With PLOP you can:

• encrypt a PDF document with user or master password, or both;
• remove PDF encryption (if you know the master password);
• add or remove permission restrictions, e.g. »text extraction not allowed« (if you know the master password);

PLOP also supports certificate security which works similar to e‑mail encryption. PDF documents can be encrypted for a number of recipients, where each recipient is identified with a certificate (public key). Only legitimate recipients can open the document with the corresponding digital ID (private key). Since certificate security is an integral part of the PDF format specification it works in Acrobat and Adobe Reader without the need for any plugin or other custom software.

Certificate security offers several advantages over password security:

• no passwords must be distributed to the document recipients;

• individual permission restrictions can be specified for each recipient or groups of recipients;

• recipients cannot pass on document passwords to unauthorized third parties.

With PLOP you can encrypt PDF documents with certificates, apply permission restrictions, and decrypt documents which are protected with certificate security (provided you have a suitable digital ID). The advantages of certificate security can be leveraged e.g. for securely distributing transaction documents or commercial content.

PLOP detects various structural PDF problems and automatically repairs the document. PLOP can also fix certain XMP problems and optionally remove damaged XMP metadata.

The PLOP library includes the pCOS programming interface for querying details about a PDF document, e.g.

• extract document info entries and XMP metadata
• list fonts and other resources
• query page sizes
• query security status, encryption scheme, permission settings
• many more PDF properties (see pCOS product description and pCOS Cookbook for more information.

PLOP also includes the pCOS command-line tool.

Metadata (»data about data«) is an important topic in many areas of application software. XMP (Extensible Metadata Platform) is an XML-based framework with many predefined metadata properties. XMP is integrated in Acrobat/PDF, and much more powerful than simple document info entries. XMP is required for PDF/A and other ISO standards. Many industry groups have published XMP-based recommendations for vertical applications.

With PLOP you can insert XMP metadata in PDF documents and extract XMP from PDF. Inserted XMP is validated to ensure correct and standard-conforming output. If the input document conforms to PDF/A or PDF/X, PLOP ensures the XMP rules set forth in the respective standard.

XMP insertion with PLOP can be used in the following and many other situations (sample XMP files are contained in the PLOP distribution):

• Add XMP metadata to PDF/A documents, including support for XMP extension schemas as defined in the PDF/A standard.
• Add XMP metadata describing the scanning process for digitized legacy documents, also according to PDF/A.
• Add XMP metadata according to the Ghent Workgroup (GWG) Ad Ticket scheme.
• Add company-specific XMP metadata.

With PLOP you can add new document information entries or replace the values of existing info entries. Both predefined and custom entries can be set. If the input document contains XMP document metadata, all predefined info entries are synchronized to the XMP metadata in order to keep the metadata consistent (this is a requirement of PDF/A).

PLOP supports all relevant PDF versions and standards:

• PLOP processes all PDF versions up to Acrobat DC, i.e PDF 1.7 (ISO 32000-1) up to extension level 8. PLOP can also process documents according to the standard PDF 2.0 (ISO 32000-2).
• PLOP is aware of the PDF/A-1/2/3 (ISO 19005) archiving standards: if the input document conforms to PDF/A, the output document is guaranteed to conform as well. PLOP fully supports XMP extension schemas as required by PDF/A. The ability to insert PDF/A-conforming XMP metadata in PDF documents is an important advantage of PLOP.
• Similarly, PLOP is aware of the PDF/X-1a/3/4/5 (ISO 15930) print production standards, PDF/VT-1/2 (ISO 16612-2) for variable and transactional printing and PDF/UA-1 (ISO 14289) for accessible PDF.

PLOP is available as a programming library (component) for various development environments, and as a command-line tool for batch operations. Library and command-line tool offer similar features, but are suitable for different deployment tasks.

The PLOP programming library is used for integration into your desktop or server application. Examples for using the library with all supported language bindings are included in the PLOP package. Since the PLOP library accepts PDF input documents from a disk file or directly in memory, it can easily be combined with other products.

The PLOP command-line tool is suited for batch processing PDF documents. It doesn’t require any programming, but offers powerful command-line options which can be used to integrate it into complex workflows. The PLOP command-line tool can also be called from environments which do not support the use of the PLOP library.

PDFlib PLOP is everywhere – it runs on practically all computing platforms. We offer 32-bit and 64-bit packages for all common flavors of Windows, macOS, Linux and Unix, as well as for IBM zSeries mainframe systems. Versions for iOS and Android are also available.

The PLOP core is written in highly optimized C and C++ code for maximum performance and small overhead. Via a simple API (Application Programming Interface) the PLOP functionality is accessible from a variety of development environments:

• COM
• C and C++
• Java
• .NET and .NET Core
• Objective-C
• Perl
• PHP
• Python
• Ruby

The extended version PLOP DS supports all features of PLOP plus the ability to apply digital signatures to PDF documents. Please see the separate PLOP DS pages for more information.