PDFlib PLOP – PDF Linearization, Optimization, Protection


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.

Linearization. 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.

Optimization. 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.

Password Security. 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);

Certificate Security. 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;
  • 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.

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

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 the datasheet for the pCOS product).

XMP Metadata. 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-1 documents, including support for XMP extension schemas as defined in the PDF/A-1 standard.
  • Add XMP metadata describing the scanning process for digitized legacy documents, also according to PDF/A-1.
  • 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).

PLOP Library and Command-Line Tool. PLOP is available as a programming library (component) for various development environments, and as a command-line tool for batch operations. The library and the 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. The PLOP command-line tool is suited for batch processing PDF documents.

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, Mac OS, Linux and Unix. Versions for mobile and embedded systems are available on request. The PLOP core is written in highly optimized 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.


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