# PDF Grid Generator Script

This script takes a PDF file and arranges it into a grid of specified rows and columns, with an optional margin applied to each page. The final output is a centered and optionally cropped PDF.

## Requirements

Ensure the following programs are installed on your system:

- **pdfjam**: A tool to manipulate PDF files, typically available via your package manager.
- **pdfcrop**: A utility to crop PDF files, often included with TeX Live.
- **pdfinfo**: A command-line utility to extract information from PDF files, part of the `poppler-utils` package.
- **pdfcropmargins**: A Python package to adjust the margins of a PDF. It's recommended to install this using `pipx`.

### Installing pdfcropmargins

It's recommended to use `pipx` to install `pdfcropmargins` to avoid conflicts with your system Python packages:

```bash
pipx install pdfcropmargins
```

If you don't have `pipx` installed, you can install it with:

```bash
python3 -m pip install --user pipx
python3 -m pipx ensurepath
```

Or, alternatively, install `pdfcropmargins` directly with `pip` (not recommended):

```bash
pip install pdfcropmargins
```

## Usage

To run the script, use the following command:

```bash
./pdf-jammer.sh input.pdf rows columns [margin]
```

### Arguments:

- `input.pdf`: The path to the input PDF file.
- `rows`: The number of rows in the output grid.
- `columns`: The number of columns in the output grid.
- `[margin]`: (Optional) The margin to apply around each page, in centimeters. Defaults to `0` if not provided.

### Example:

```bash
./pdf-jammer.sh example.pdf 2 3 1
```

This command arranges the `example.pdf` into a grid of 2 rows and 3 columns with a 1 cm margin around each page.

## Output

The script generates a centered PDF with the filename `jammed.pdf` in the current directory.

## Error Handling

The script includes error checks to ensure the required programs are installed and that the `pdfjam` and `pdfcropmargins` commands succeed. If an error occurs, the script will exit early with a relevant message.

## License

This script is provided "as-is" without any warranty. Use it at your own risk.