What are the best PDF SDKs?

ComPDFKit, a software development kit (SDK), consists of PDF SDK and PDF Conversion SDK. With this SDK, even developers with limited knowledge of PDF can quickly integrate professional PDF functions with just a few lines of code on multiple platforms. Following are the key features of ComPDFKit. Viewer: - Standard page display modes, including Scrolling, Double page, Crop mode, and Cover mode. - Navigation with thumbnails, outlines, and bookmarks. - Text search & selection. - Zoom in and out. - Switch between different themes, including Dark mode, Sepia mode, Reseda mode, and Custom color mode. - Text reflow. Annotations: - Create, edit and remove annotations, including Notes, Link, Freetext, Line, Square, Circle, Highlight, Underline, Squiggly, Strikeout, Ink, and Stamp. - Support for annotation appearances. - Import and export annotations to/from XFDF. - Support for annotation flattening. Forms: - Create, edit and remove form fields, including Push Button, Check Box, Radio Button, Text Field, Combo Box, List Box, and Signature. - Fill PDF Forms. - Support for PDF form flattening. Document editor: - PDF manipulation, including Split pages, Extract pages, and Merge pages. - Page edit, including Delete pages, Insert pages, Move pages, Rotate pages, Replace pages, and Exchange pages. - Access document information. - Extract images. Security: - Encrypt and decrypt PDFs, including Permission setting and Password protected. - Create, edit, and remove watermark. - Redact content including images, text, and vector graphics. - Create, edit, and remove header & footer, including dates, page numbers, document name, author name, and chapter name. - Create, edit, and remove bates numbers. - Create, edit, and remove background that can be a solid color or an image. Conversion: - PDF to Word. - PDF to Excel. - PDF to PPT. - PDF to TXT. - PDF to CSV. - PDF to PDF/A.