The Impact of PDF Page Structure on the Efficiency of Digital Layout Work

In the digital layout (referred to as imposition) operation, the physical properties of the PDF pages, the bleeding patterns, and the page size are the key factors affecting the layout and positioning of PDF pages on large layouts. PDF pages with full specification page structure can adopt a unified and efficient layout and positioning method when the layout is applied. Non-standard page structure requires a variety of processing schemes. It is labor-intensive, inefficient and error-prone. This paper analyzes the structure of PDF pages, and combines Signastation software to summarize the positioning method of different structured PDF pages in the layout. At last, from the aspect of standardizing PDF page design and specification page preprocessing, the paper puts forward a strategy to improve the efficiency of large-scale layout operations. .

I. PDF page structure

The attributes of the PDF page composition, page bleeding, and page size are the main factors affecting the structure of the PDF page.

1.PDF page composition

In general, when a PDF page is created using software such as Indesign, Illustrator, or Acrobat, a complete PDF page consists of a Media Box, a Trim Box, a Crop Box, and a Bleeding Box ( Bleed Box and Art Box are composed of five physical boxes.

1 Media Box. The media box is the largest box on the page and contains all the objects of a page, including text, pictures, and tags on the page. The media box defines the scope of physical media that needs to be printed on the page. In addition to graphic content, it also includes crop marks, color bars, and so on.

2 Finished trim box (Trim Box). The finished trim box determines the final effective size of the page after printing and cutting. The finished trim box corresponds to the actual size of the page (finished product size). If a PDF document contains a trim box, the size of the trim box is the same as the final finished product.

3 Crop Box: defines the section to be trimmed after the page is displayed or printed out. Unlike other boxes, it has no physical page geometry meaning, and the Crop Box is smaller than the Media Box.

4 Bleed Box. The Bleed box is outside the page crop marks. All page sections between the Bleed Box and the Trim Box will be trimmed at the end.

5 Content Box (Art Box). If a PDF page is to be placed in an application, the Art Box will determine the area of ​​the page to be placed.

2. PDF page bleeding

PDF page bleeding is also different due to the prepress design requirements and habits, there are generally the following situations (in the finished product size of 210 × 285mm 16 open as an example, a single side bleeding is 3mm.):

1 Trilateral bleeding. That is, the head, foot, and incision are each bleeding 3mm. If the mouth is not bleeding, the PDF page size is 213×291mm.

2 bleeding on all sides. That is, each head, foot, incision, and mouthpiece bleeding 3mm, then the PDF page size is 216 × 291mm.

3 does not bleeding. This situation is generally the content of books and magazines, leaving the four sides empty, no bleeding, the size of a single page is 210 × 285mm.

3.PDF page size

1 single page file. The size of the PDF page at this time is the finished product size plus the bleeding size.

2 cross-page documents. The size of the PDF page at this time is twice the size of the single-page document, depending on the finished product size and the bleeding pattern. For example, two open pages with a size of 210 × 285mm will be combined into a cross-page document. If three-sided bleeding is used, the file size is 426 × 291mm.

In prepress production, the actual PDF page structure differs depending on the knowledge, experience, and habits of prepress designers and the degree of prepress job management. Some PDF pages are very standard, including the media box, the Trim Box, the Bleed Box, and other structural frames, and the bleeding patterns and dimensions are the same (if they are all four-sided 3mm bleeds. Pages); some are not standardized, do not define any structural boxes, and the size and manner of bleeding are inconsistent. The non-standard PDF page structure increases the prepress processing workload and the probability of errors.

Second, layout layout of the PDF page layout

1. Large format layout

The large format layout is based on many factors such as printer size, plate size, paper size, and PDF page structure. The large format structure defined in Signastation software includes platen bite, paper bite, home page (PDF page), gutter, cutting line and various marks. The home page is used for layout positioning of PDF pages on the large version, which is divided into left home page and right home page. The home page size is determined by the actual size (finished product size) and the size of the bleeding.

2. Positioning of PDF pages

According to the structure of the PDF page in the layout, the layout of the homepage is defined in the layout software, and the method of page positioning is determined, including the type of the homepage, the actual size (finished product size), the setting of the bleeding size, and the size of the page displacement. With directions and so on.

For different PDF page structures, there are two page positioning schemes in Signastation: automatic and user-defined.

1 Automatic: The system automatically puts pages into the large version file based on the PDF page structure. The rules are as follows:

If the PDF page contains a Trim Box, align the lower left corner of the trim box with the bottom left corner of the finished dimension of the home page; if there is no Trim Box, there will be a Crop Box (Crop Box) ), the lower left corner of the Crop Box is aligned with the lower left corner of the finished product on the homepage; if there is neither a Trim Box nor a Crop Box, there is a Media Box, Align the lower left corner of the media box with the lower left corner of the actual size of the home page.

2 User Defined: Allows users to accurately position PDF pages by setting page offsets. The most important parameter here is Offset. The offset refers to the offset value of the origin of the PDF page relative to the origin of the large version of the homepage. There are three methods for setting the offset.

From the trim box: The trim box here refers to the Trim Box. At this time, the origin of the PDF page coordinates is in the lower left corner of the crop box, and the origin of the home page is in the lower left corner of the finished product size. The imposition system can automatically recognize the coordinates and align them without displacement. This method is equivalent to the "automatic" approach.

Centering: PDF pages are centered on the home page. This applies to PDF pages that have a consistent bleeding pattern.

Customization: It is mainly used for PDF pages that are not equipped with trim boxes, bleed boxes, etc. Need to set the X, Y direction of displacement to achieve the positioning of the PDF page.

Offset X: The distance from the origin of the PDF page to the home origin offset in the X direction (horizontal direction). Offset Y: Offset of the PDF page origin in the Y direction (horizontal direction) relative to the homepage origin.

3 page positioning examples

Take a cross-page file as an example. Assume that the finished product size is 210 × 285mm, the PDF page is a cross-page document, and the single-page three-sided bleeding is 3mm on each side. The PDF cross-sheet file size is 426 × 582mm, and the Trim Box is not set on the PDF page. . There are two ways to handle this type of page layout:

1 Method 1: Split the cross-page file into a single page file, set the left and right home pages for the single-page file, and perform the X, Y direction displacement. The page after splitting is three-sided and the size is 213×291mm; the displacement of the left page is (X:-3mm, Y:-3mm), and the displacement of the right page is (X:0mm, Y:-3mm) .

2 Method 2: Do not split the cross-page file and use the displacement to locate it. At this time, the displacement value of the left page is (X: -3 mm, Y: -3 mm), and the displacement of the right page is (X: -213 mm, Y: -3 mm).

Different page positioning methods are required for other PDF page structures, which increases the variability and complexity of the imposition job, reduces the reliability of the imposition job, and then affects the normal operation of the post-press processing operations. Therefore, how to standardize the structure of PDF pages, simplify layout work, and improve reliability and efficiency are issues that are worthy of attention in prepress operations.

Third, standardized PDF page structure to improve the efficiency of the layout of the strategy

1. Specification PDF page design

Develop a standard homework manual on PDF page design, train employees, communicate with customers, and hope that employees and customers can design PDF pages in accordance with standardized requirements. There are:

1 In InDesign and Illustrator software, create page frames such as Media Box, Trim Box, and Bleed Box for PDF pages.

2 Set the bleeding edge for the PDF page when setting the page properties, and unify the bleeding size.

2. Use Acrobat and Pitstop software specification PDF page processing

For non-standard PDF pages, use Acrobat and Pitstop software to process them before the imposition. These are:

1 Pages for three-sided bleeding In Acrobat, the page is treated as four-sided bleeding by increasing the page size.

2 For cross-page documents, the page should be split into a single page file before the layout job.

3 In the Pitstop, add page frames such as Media Box, Trim Box, and Bleed Box to the page. In this way, the software can automatically identify the page structure frame and automatically locate it during the layout.

3. Use of standard layout software

For different PDF pages, a unified PDF page positioning template is set up in the imposition software to form a job specification so that different operators have the same operation method.

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If there is no need for waterless or dry offset printing, the damper system's bridge roller must be replaced with a non-shake type. After the ink key setting is complete, the press is ready. It only takes 5-10 minutes for the operator to prepare the rainbow printing system. The rainbow printing device is designed and developed according to our customers' special needs. In the production of long-lived jobs, such as over 10,000 impressions, we recommend the use of a special ink fountain roller with a circumferential groove to prevent ink bleeding.

Rainbow printing technology is now widely used in Heidelberg Speedmaster SM 52, SM 74, XL75, CD 102 and SM 102 series products. In 2007, the world’s largest banknote printing company, China Banknote Printing and Coinage Corporation, installed 12 Heidelberg Speedmaster CD 102 presses at its six branches in the mainland, all of which were equipped with rainbow printing. system. In Europe and the United States, manufacturers specializing in security printing are also using Heidelberg's rainbow printing technology. In July 2010, the 150th Heidelberg printing unit equipped with a rainbow device settled in a Russian special security printing company along with the Speedmaster SM 102 six-color UV offset press. A Dutch printing plant also recently started using their first Speedmaster XL 105 offset press equipped with a rainbow printing system.

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