### Create a Simple PDF File with HexaPDF

Source: https://github.com/gettalong/hexapdf/blob/master/README.md

This example demonstrates how to create a basic PDF file with text using the HexaPDF library. Ensure the 'hexapdf' gem is installed.

```ruby
require 'hexapdf' 

doc = HexaPDF::Document.new
canvas = doc.pages.add.canvas
canvas.font('Helvetica', size: 100)
canvas.text("Hello World!", at: [20, 400])
doc.write("hello-world.pdf")
```

--------------------------------

### Template File Format Example

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

An example illustrating the format of a template file used for filling PDF form fields. Field names are listed at the beginning of lines, followed by their values. Values can span multiple lines.

```text
page1.field1: A simple value
page1.field3: Another value
  spanning more than on
  line.

Another form field:
  Value for this form field.
```

--------------------------------

### Recursive Object Inspection Example

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Demonstrates the output format for recursively inspecting an indirect object. It shows how references are replaced with custom indices and how page objects are identified.

```text
<<
  /Info {obj 1} <<
    /Producer (HexaPDF version 0.9.3)
  >>
  /Root {obj 2} <<
    /Pages {obj 3} <<
      /Count 1
      /Kids [{obj page 1} <<
        /MediaBox [0 0 595 842 ]
        /Parent {ref 3}
        /Type /Page
      >> ]
      /Type /Pages
    >>
    /Type /Catalog
  >>
  /Size 4
>>
```

--------------------------------

### Inspect a PDF file

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Shows the page object for the first page as well as the decoded content stream of the first page. Starts the interactive inspection mode.

```bash
hexapdf inspect input.pdf
```

--------------------------------

### CombinePDF Invocation

Source: https://github.com/gettalong/hexapdf/blob/master/benchmark/optimization/README.md

Example of how to invoke the CombinePDF script for merging PDF files. This script is written in Ruby.

```bash
ruby combine_pdf.rb INPUT OUTPUT
```

--------------------------------

### Convert Images to PDF with Page Size and Margins

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Creates a PDF with specified page size (A4) and margins (36pt) around each image. Images are fitted to the pages.

```bash
hexapdf image2pdf -p A4 -m 36 image1.jpg image2.pdf image3.png output.pdf
```

--------------------------------

### Get General Information about a PDF File

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Reads a PDF file and displays general information such as author details, PDF version, and encryption status.

```bash
hexapdf info input.pdf
```

--------------------------------

### QPDF: Object Streams (CS)

Source: https://github.com/gettalong/hexapdf/blob/master/benchmark/optimization/README.md

Invoke qpdf with the --object-streams=generate option to enable object streams (S) in addition to compacting (C).

```bash
qpdf --object-streams=generate INPUT OUTPUT
```

--------------------------------

### Executing a Single Command on Multiple Files

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Applies the 'info' command to multiple PDF files, outputting information for each.

```bash
hexapdf batch 'info {}' input1.pdf input2.pdf input3.pdf
```

--------------------------------

### Check PDF for Errors and Get Information

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Checks a PDF file for parse and validation errors, prints them, and then displays general information. HexaPDF can still handle the file even if errors are found.

```bash
hexapdf info --check input.pdf
```

--------------------------------

### Apply watermark from a PDF

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Uses the first page of watermark.pdf as a background for all pages of input.pdf and saves the result to output.pdf.

```bash
hexapdf watermark -w watermark.pdf input.pdf output.pdf
```

--------------------------------

### QPDF: Standard Mode (C)

Source: https://github.com/gettalong/hexapdf/blob/master/benchmark/optimization/README.md

Invoke qpdf for standard PDF transformation, which includes the 'C' operation (Compacting).

```bash
qpdf INPUT OUTPUT
```

--------------------------------

### Merge PDFs Starting with an Empty File

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Merges pages from three input files into a new, empty PDF. The output file will only contain the merged pages without any meta data from the input files.

```bash
hexapdf merge -e input1.pdf input2.pdf input3.pdf output.pdf
```

--------------------------------

### Attach Files with Descriptions to PDF

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Attaches multiple files to a PDF and saves the result to a new output file. Allows specifying descriptions for attached files.

```bash
hexapdf files -a invoice.xml -d "Invoice data" -a custom.xml input.pdf output.pdf
```

--------------------------------

### Apply watermark as stamp with specific pages

Source: https://github.com/gettalong/hexapdf/blob/master/man/man1/hexapdf.1.md

Applies the first page of watermark.pdf as a stamp to the first page of input.pdf, and the second page of watermark.pdf to all other pages of input.pdf.

```bash
hexapdf watermark -w watermark.pdf -i 1,2 -t stamp input.pdf output.pdf
```

--------------------------------

### HexaPDF: Full Optimization (CSP)

Source: https://github.com/gettalong/hexapdf/blob/master/benchmark/optimization/README.md

Invoke hexapdf with all optimization flags enabled: Compacting (C), Object Streams (S), and Page Recompression (P).

```bash
hexapdf optimize INPUT --compress-pages OUTPUT
```