PDF (Portable Document Format)

PDF (Portable Document Format) - Cross-platform format of electronic documents. Developed by Adobe Systems using the PostSoundPage ^[1]

One method of creating PDF documents is a virtual printer - a document, as such, is prepared in its specialized program - a graphic application or a text editor, CAD, etc., then exported to PDF format for distribution in electronic form, transfer to a printing house, etc.

To view PDF files, there are many programs and the official Adobe Reader program. A significant amount of modern professional printing equipment has hardware support for PDF format, this allows you to print documents without the use of any software.

History

PDF was created by Adobe in 1992. Over the next 20 years, the portable document format (PDF) became an open standard for the exchange of electronic documents, it was recognized by the International Organization for Standardization (ISO).

At the first time of its existence, it was not popular:

• Adobe's software for reading and creating PDF was paid;
• there was no support for external references;
• PDF documents were cumbersome compared to plain text;
• The display of the PDF document on machines with low performance required patience from users.

There were several competing formats: Envoy, Common Ground Digital Paper, Farallon Replica and was PostScript even a competitor.

Functionality

A PDF file is often presented as a combination of text with raster and vector graphics, less often - text with forms, Javascript scripts, 3D graphics and other types of elements. The volume of two PDF documents that look the same on the screen may differ. It depends on:

• embedding or linking fonts and multimedia;
• raster image resolutions
• Use the built-in compression mechanism for the entire document
• raster image compression algorithms used.

To create a minimum volume document, you must use vector graphics and "safe" fonts, which have 14, in their composition:

• Times (v3) (normal, italic, bold and bold italic)
• Courier (normal, sloping, bold and bold sloping)
• Helvetica (v3) (normal, oblique, bold and bold oblique)
• Symbol
• Zapf Dingbats

You can use these fonts without embedding them in the document because all programs must display them correctly on the screens. Any other fonts that are not embedded in the document and are not present in the system will be replaced by one of the available fonts, which can cause an increase or decrease in the number of pages, the number of characters in the line, line spacing, and other display errors associated with the font metric.

There are a number of software products available to edit files in this format.

Documents, forms, graphics, and web pages converted to PDF do not differ from printed documents, but unlike paper documents, PDF files can contain links and interactive interface elements that are activated using the mouse, form fields, embedded video and audio data, logical diagrams that help automate typical business processes. The contents of the PDF file can be read by anyone using Adobe Reader free software or Adobe Reader mobile applications.

PDF allows you to embed the necessary fonts that change the textual appearance, vector and bitmap images, forms, and multimedia inserts. Supported color profiles are RGB, CMYK, Grayscale, Lab, Duotone, Bitmap, several types of raster information compression. There are own technical formats for graphic arts: PDF/X-1, PDF/X-3. The security mechanism is represented by electronic signature capabilities. A large number of related documents are distributed in PDF format.

PDF Document Standard

On July 1, 2008, PDF became the open standard ISO 32000.

Advantages

• Trust. Throughout the world, PDF is used as a standard that ensures a significant level of document security. Files in this format:
  • can be password protected
  • can prevent outsiders from accessing PDF documents,
  • prevent them from being copied, modified, or printed.
  • Sensitive information can be deleted from PDF documents.

• Support for different platforms. Interaction with PDF documents is possible on almost any platform, including Windows, Mac and mobile platforms - Android and iOS for iPhone and iPad.

• Maintaining file integrity. PDF documents look the same as source files, store all the information contained in them even when text, pictures, video, audio, 3D maps, full-color graphics, photos and business logic are combined into one file or PDF portfolio.

• Simplicity of signature. Any user can sign the PDF electronically using the free Adobe Reader XI or Adobe Reader mobile software. PDF provides support for conventional digital signature images certified by independent certification authorities.

• Search capability. It is easy to search the file for text or metadata, including scanned text converted using optical character recognition (OCR) technology.

• Extended Access. PDF files are more accessible to people with disabilities (poor vision or blindness).

• Widespread.

Adobe PDF Specifications

• 1993 — PDF 1.0 / Acrobat 1.0
• 1994 — PDF 1.1 / Acrobat 2.0
• 1996 — PDF 1.2 / Acrobat 3.0
• 2000 — PDF 1.3 / Acrobat 4.0
• 2001 — PDF 1.4 / Acrobat 5.0
• 2003 — PDF 1.5 / Acrobat 6.0
• 2005 — PDF 1.6 / Acrobat 7.0
• 2006 — PDF 1.7 / Acrobat 8.0
• 2006 — PDF 1.7 / Acrobat 8.2
• 2008 — PDF 1.7, Adobe Extension Level 3 / Acrobat 9.0
• 2009 — PDF 1.7, Adobe Extension Level 5 / Acrobat 9.1

Adobe PDF Versions

PDF for long-term archival storage of electronic documents - PDF/A

PDF/A (English Portable Document Format/A) - ISO 19005-1: 2005 standard (published October 1, 2005) for long-term archival storage of electronic documents. The basis is a description of the PDF standard version 1.4 from Adobe Systems Inc. (used in Adobe Acrobat 5).

PDF/A is a subset of PDF format that excludes features that do not meet data requirements for long-term archival storage. Implemented similar to PDF/X.

Key elements of PDF/A compliance:

• Prohibit embedding audio and video
• It is not allowed to embed code on Javascript and commands to start executable files.
• All fonts must be embedded and legally implemented for unlimited universal display. This also applies to the so-called standard Postscript fonts - Times or Helvetica.
• Color spaces are defined in a device-independent manner.
• Encryption is not allowed.
• The use of metadata based on standards is prescribed.

2022: Hackers have found a way to infect computers with a virus using pdf files

In mid-May 2022, it became known that on the Internet they began to increasingly use pdf documents to hack computers. The HP Wolf Security report says how hackers with their help have learned to access almost any computer.

According to the report of HP Wolf Security, an email is sent to users with a message about an ambulance payment in the name of the owner of the mail. Attached to the email is a pdf file. Opening a file on a personal computer allows hackers to remotely launch malicious software using a link inside the document.

Researchers found that trying to open a pdf through Adobe Reader will lead to the user being invited to use the Microsoft Word text editor, since the docx file is contained inside. Hackers were able to hide the virus for security systems and the open document will be indicated as verified.

Attackers in attacks use the vulnerability CVE-2017-11882, fixed in November 2017. In OMicrosoft Office, there is a vulnerability to remote code execution when the software cannot properly process objects in memory. A hacker who successfully exploits a vulnerability can run arbitrary code in the context of the current user. If the current user is logged on as an administrator, the attacker may gain control of the vulnerable system. Then the attacker can install programs, view, modify or delete data, or create new accounts with full user rights. Users whose accounts have fewer user privileges on the system may be less affected than users who work with administrator privileges. In, security software eliminates vulnerabilities by correcting how objects in memory are handled by a vulnerable Office component.

Microsoft Office has a vulnerability to remote code execution when the software cannot properly process objects in memory. An attacker who successfully exploits a vulnerability can run arbitrary code in the context of the current user. If the current user is logged on as an administrator, the attacker can gain control of the vulnerable system. The attacker can then install the software; View, edit, or delete data or create new accounts with full user privileges. Users whose accounts have fewer user privileges on the system may be less affected than users who work with administrator privileges.

HP Wolf Security experts stated that many users did not download the necessary update for their operating systems. Malicious objects of this family exploit the vulnerability of Microsoft Equality Editor (a component of Microsoft Office). If the attack is successful, the attacker can execute his code on behalf of the user. Researchers have shown how attackers use pdf documents to infect systems. Embed files, download remotely hosted exploits, and encrypt shell code:

• REMMITANCE INVOICE.pdf

05dc0792a89e18f5485d9127d2063b343cfd2a5d497c9b5df91dc687f9a1341d

• has been verified. however pdf, jpeg, xlsx,.docx

250d2cd13474133227c3199467a30f4e1e17de7c7c4190c4784e46ecf77e51fe

• f_document_shp.doc

165305d6744591b745661e93dc9feaea73ee0a8ce4dbe93fde8f76d0fc2f8c3f

• f_document_shp.doc_object_00001707.raw

297f318975256c22e5069d714dd42753b78b0a23e24266b9b67feb7352942962

• Exploit shellcode

f1794bfabeae40abc925a14f4e9158b92616269ed9bcf9aff95d1c19fa79352e

• fresh.exe (Snake Keylogger)

20a3e59a047b8a05c7fd31b62ee57ed3510787a979a23ce1fde4996514fae803

• External OLE reference URL

hxxps://vtaurl[.]com/IHytw

• External OLE reference final URL

hxxp://192.227.196[.]211/tea_shipping/f_document_shp.doc

• Snake Keylogger payload URL

hxxp://192.227.196[.]211/FRESH/fresh.exe

• Snake Keylogger exfiltration via SMTP

^[2]

2014: Using PDF in Russia

On September 30, 2014, Abbyy Russia announced the completion of a study of the PDF document market in Russia and scenarios for working with PDF documents.

How PDF is used in Russia

The survey was attended by 500 office employees from Moscow, St. Petersburg and a number of cities working in various sectors of the public and private sectors. According to this document, in 2014, respondents noted an increase in the volume of documents in PDF format. Even the results of the study made it clear that the transition to electronic document management did not occur everywhere: 68% of office employees believe that the flow of paper documents has increased.

The most common PDF document scenarios are:

• 62% of respondents often look for information in PDF text;
• 60% copy text from PDF;
• 54% regularly work with pages in the document:
  • change their order,
  • add new
  • remove existing ones;

• 52% make minor edits to the PDF text, correct errors or typos;
• 46% combine files of different formats into a single PDF.

Links

• Portable Document Format
• About Adobe PDF File Format
• PDF/A

Notes