PDFlib PLOP (PDF Linearization, Optimization, Protection) is a versatile tool for linearizing, optimizing, repairing, analyzing, encrypting and decrypting 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 access permissions 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 restrictions, e.g. »printing not allowed« or »text extraction not allowed« (if you know the master password);
  • query information about the security status (encrypted with user or master password), encryption scheme, permission settings, and document info fields

Repair Mode

Various kinds of damaged PDF documents are detected and automatically repaired.

PDF Analysis

The PLOP library includes the pCOS interface for querying details about a PDF document, such as document info and XMP metadata, font lists, page size, and many more (see separate datasheet for the pCOS product).

XMP Metadata

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.

Document Info Entries

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).

PDF Versions and Standards

PLOP supports all relevant PDF versions and standards:

  • PLOP processes all PDF versions up to Acrobat XI, i.e PDF 1.7 (ISO 32000-1) up to extension level 8. PLOP can also process documents according to the forthcoming 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 transactional printing and PDF/UA-1 (ISO 14289) for accessible PDF.

PLOP Library or Command-Line Tool?

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.

Supported Development Environments

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, OS X, Linux and Unix, as well as for IBM i5/iSeries and zSeries systems. Versions for mobile and embedded systems are available on request.

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 for use with VB, ASP, Borland Delphi, etc.
  • C and C++
  • Java, including servlets and Java Application Server
  • .NET for use with C#, VB.NET, ASP.NET, etc.
  • Objective-C
  • Perl, PHP, Python, Ruby

PLOP DS for digitally signing PDF

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.


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