PDF files have layers, you do not use?

PDF format files

Today, the delivery of electronic documents, especially cross-company document exchange, the use of PDF format is increasing.

PDF format files are characterized as follows:

1. Application version-independent: PDF format files can be compatible with different versions of the application, such as AutoCAD files, either the 2007 version or the 2014 version, the lower version of the program can not open the higher version of the saved format.merge pdf files i love pdf The use of PDF format for delivery, will not be affected by the application version.

2. No need to install specialized applications: PDF format files do not need to install specialized applications, such as Solidworks, PKPM, PS, Project, etc.. As long as the installation of the PDF viewing program, you can even use the browser to open the file directly.

3. to solve the problem of missing fonts: for some special departments or design institutes and other documents produced by the company, they may use a number of specialized fonts. In the source file delivery, due to the inability to carry the font file, the receiver may open the file when the missing fonts. And in AutoCAD and Word documents, this often happens, although alternative fonts may be used, but at least it may also lead to changes in typographic formatting.

4. Preserve special commands and data references: Some programs have special commands, such as the reference and attach commands in AutoCAD. These commands may not be bound to the file, and thus may appear incompletely displayed when the recipient opens the source file. Similarly, Excel may also refer to other files of data, if the transfer of the source file is not synchronized with the transfer of the referenced data files, may lead to data errors.

5. Protect the author's copyright: PDF documents can only be used to view, although you can use specialized software for a small amount of editing, but can not be as easy as Word as large-scale copying, editing and reformatting. This protects the author's copyright to a certain extent.

6. WYSIWYG: the use of PDF file format for delivery can ensure that the receiver to see the content of the original content with the same.

7. similar to the image format: in a sense, PDF format files like image format files, mainly for viewing, in general, you can only view the operation.

For most students, the knowledge of PDF documents may be limited to the above points.

Scanned version of the double layer PDF

We often find a phenomenon, obviously the PDF file is a scanned version, but you can copy the text. This is because PDF production uses a technology called "double layer PDF".

Double PDF format is a derivative form of PDF documents, which is characterized by the document can be both text-based (such as documents generated by Word), can also be image-based.