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Asked: 2024-09-21T16:11:48+05:30 In:

I need assistance with creating a Node.js Lambda function that modifies a PDF document. I am considering using either PDF-lib or PDFKit for this task. Can anyone provide insight into how to approach this, including any relevant examples or best practices?

Hey everyone!

I hope you’re all doing well! I’m currently working on a project where I need to create an AWS Lambda function using Node.js, and my goal is to modify PDF documents. I’ve been looking into two libraries, PDF-lib and PDFKit, but I’m not quite sure which one would be the better choice for my use case.

Here’s what I’m trying to achieve: I need to be able to add text to existing PDFs, adjust images, and possibly merge multiple PDFs into one. I’d love to hear your experiences with either of these libraries.

– Have any of you used PDF-lib or PDFKit for similar tasks in a Lambda function?
– Which one do you think would be more suitable for handling PDFs in a serverless environment?
– Any code snippets or examples would be greatly appreciated, especially if you could share best practices for optimizing performance and managing Lambda’s execution limits.

Thanks so much in advance! Your insights would really help me out. Looking forward to your responses!

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    1 Answer

    1. Hey there!

      Hope you’re doing well too! I recently worked on a similar project that involved modifying PDFs using AWS Lambda with Node.js, so I’m happy to share my experience with both PDF-lib and PDFKit.

      1. **Library Choice**: Between PDF-lib and PDFKit, I found **PDF-lib** to be a better fit for your use case. PDF-lib provides a more straightforward API for modifying existing PDFs, which is great for adding text and adjusting images. It also supports merging PDFs, making it versatile for your needs. PDFKit is more focused on creating PDFs from scratch, which might not be as beneficial since you’re looking to modify existing files.

      2. **Lambda Environment**: Both libraries can work in a serverless environment like Lambda, but I found PDF-lib to have a lighter footprint, which is crucial for performance. It also avoids some of the complexities that can come with PDFKit, especially when dealing with dependencies for image handling.

      3. **Code Snippets**: Here’s a simple example of how you can use PDF-lib to add text and mix multiple PDFs:

      “`javascript
      const { PDFDocument, rgb } = require(‘pdf-lib’);
      const fs = require(‘fs’);

      exports.handler = async (event) => {
      // Load a PDF document
      const existingPdfBytes = await fetch(‘https://example.com/yourfile.pdf’).then(res => res.arrayBuffer());
      const pdfDoc = await PDFDocument.load(existingPdfBytes);

      // Add text to PDF
      const page = pdfDoc.getPage(0);
      page.drawText(‘Hello, world!’, {
      x: 50,
      y: 700,
      size: 30,
      color: rgb(0, 0, 0),
      });

      // Merge with another PDF (assuming you’ve loaded the second PDF similarly)
      const secondPdfBytes = await fetch(‘https://example.com/secondfile.pdf’).then(res => res.arrayBuffer());
      const secondPdfDoc = await PDFDocument.load(secondPdfBytes);
      const secondPage = await pdfDoc.copyPages(secondPdfDoc, [0]);
      pdfDoc.addPage(secondPage[0]);

      // Serialize the PDF document to bytes (for storage or response)
      const pdfBytes = await pdfDoc.save();

      // Save or return the pdfBytes here
      return pdfBytes;
      };
      “`

      4. **Performance Optimization**: A couple of best practices for Lambda functions:
      – **Memory Allocation**: Ensure your Lambda function has sufficient memory allocated; this directly affects its CPU power as well. More memory can lead to faster execution times.
      – **Cold Starts**: If you’re concerned about cold starts, consider keeping your Lambda function warm with a scheduled event, especially if it’s not being triggered frequently.
      – **Avoid large PDF uploads**: If your PDFs are large, consider S3 for initial uploads and keep processing lightweight to avoid hitting execution time limits.

      Feel free to ask if you have more questions or need clarification on anything! Good luck with your project!

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