The third file naming option is Merge files based on common prefix, use prefix as file name. Use this merging mode if your input files already have a naming convention, where the file name contains a prefix and a page number, such as Chapter1_001.tif thru Chapter1_099.tif. All the input files having the same common prefix will be merged into a single PDF file that will be named the same way as the common prefix. It is possible that a directory has files with different common prefixes. In this case, multiple output PDF files will be created in the same directory, as many of them as many different prefixes you have in your input folder.

Different people use different naming conventions. The most common convention is to use a prefix, then a page number, such as Prefix005.tif. If the prefix itself ends with a number, then you have to use a separator, so you can separate the prefix from the number, such as Chapter1_005.tif. If you have this naming convention, where the file name without the extension ends with a number, then ELAN Converter™ can automatically recognize your common prefix. The common prefix is the file name without the extension and without the decimal numbers at the end. If there is a separator mark, such as an underscore (_), a dot (.), or a hyphen (-), that will be chopped off too. For example, the common prefix in Chapter1_005.tif is "Chapter1", and the common prefix in 01-publication-100.tif is "01-publication". To use this automatic prefixing, choose the Automatic (prefix is file name without a trailing number) sub-option.

Note that you can not always use automatic prefixing. For example, if your naming does not contain numbers, but there is a separator character, you should use that separator to find the common prefix, such as in TableOfContents_A.tif, TableOfContents_B.tif, TableOfContents_C.tif. The common prefix is obviously TableOfContents. Choose the Use custom separator character sub-option in this case. If you have the separator character more than once in your file name, you should also specify the direction. For example, if your file is named like Table_Of_Contents_A.tif, then the common prefix is the portion before the last separator ("Table_Of_Contents"), not the one before the first separator (which would be "Table"). You can specify this option by selecting either from the beginning (before the first separator) or from the end (before the last separator) from the drop down list.

Sometimes you just do not have any separator character at all. For example, you could have a rule that the first 4 characters are the common prefix, and the rest is the page numbering, such as 0034001.tif, 0034002.tif, and so on. If this is the case, you should choose the last option that reads Use first N characters as a common prefix, and specify a number, such as 4 for the first 4 characters.

Please see Figure 4 for a sample job. (Notes: We assume that Subdirectory depth set to unlimited, which we will discuss a little bit later).

Figure 4. Merging by common prefix

A: Typical input directory tree; B: output tree merged by prefix

To summarize: Choose the common prefix-based merging if you have a file naming convention that describes which files belong together. The output PDF file will be named like the common prefix. The order in which the input files are added to the PDF file is based on the alphabetical order of the input file names.