Chapter.8 Limitations

Processing and editing using Antenna House PDF API has the following limitations.

8–1 PDF Versions

8–1–1 Versions Available to be Processed

PDF files that can be handled by Antenna House PDF API are files that comply with the "ISO 32000 (32000-1, 32000-2)" specifications.

8–1–2 PDF Version of Input / Output Files

You cannot specify an arbitrary PDF version number for the output PDF.
In principle, the version of the output PDF will be the same as the input PDF.
If you process multiple files as input PDF, for example by merging PDFs, the PDF version of the output file will be the same as the highest version number among the input files.
The PDF version may become larger when saving with encryption security set. (*1)

(*1) When setting encryption security, if the PDF version of the input file is smaller than the PDF version according to the specified encryption type, it will be changed to the PDF version according to the encryption type.

Encryption Type	PDF Version
128bit RC4	1.5
128bit AES	1.6
256bit AES	1.7

8–2 Limit Size on Read / Write

The maximum read/write PDF file size is 2GB. The specific restrictions are as follows.

The file size of PDF files that can be loaded as input files is up to 2GB. If the PDF file exceeds 2GB, an error will occur when loading.
The maximum file size of PDF files saved using Antenna House PDF API is 2GB. If it exceeds 2GB (*2), an error will occur when saving.

(*2) The upper limit of the output file size here is determined by whether the output PDF resulting from PDF processing and editing using Antenna House PDF API exceeds 2GB.

This specific example is the case when merging PDF files. Merging PDF files using Antenna House PDF API is not a process of physically merging PDF files. Therefore, if the merged output PDF exceeds 2GB, an error may occur even if the total PDF file size before merging is less than 2GB.

For specific PDF file merging operations, see "-mergeFiles: Merging PDF files" in this manual.

8–3 Editing PDF/A and PDF/X

If you edit a file with PDF/A-1b, PDF/A-2b, or PDF/X standards, the information on these standards will be discarded.

8–4 PDF Optimization

There are limitations when performing the following operations when optimizing PDF:

When downsampling is performed, the color space may differ from the original data.
When you merge fonts, only embedded fonts are merged. The formats that can be merged are TrueType, Type1 (CFF format only), CIDFontType2, and CIDFontType0.

For details on specifying downsampling and merging font in PDF optimization, see "-optimize: Optimizing PDF Files" in this manual.

8–5 Font Limitations

Bitmap fonts and Type3 fonts are not supported.
In vertical writing, even if italic is specified, if the font does not have glyphs, it will not become italic.

Antenna House PDF API handles fonts in processes such as inserting text watermarks and drawing text on PDF page content. The specific commands for handling fonts are as follows.

8–6 Retaining Security Information

The security information of the input PDF file is basically carried over to the output PDF file, but it is not carried over with the following exception command.

Exception command:

Security information is newly set.
"-encrypt: PDF Security Settings"
Security information will be removed
"-decrypt: Removing PDF security Settings"
Security is not carried over to the output PDF file
"-mergeFiles: Merging PDF Files"
"-pageExtract: Extracting Pages"

For details on exception command, see the explanation of associated command in "13 Parameters for Commands" in this manual.

8–7 Using Multiple Threads

The Command-line cannot be used by multiple threads at the same time.

8–8 String Limitation in Command Prompt

In Windows, there is a limit on the number of characters in the command prompt. Be careful when using the Command-line.

Reference: Command prompt line string limitation - Windows Client | Microsoft Learn

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